David Guretzki's An Explorer's Guide to Karl Barth is a hitchhiker's guide to Karl Barth for the average joe. Karl Barth is notoriously difficult to epitomize and summarize, and other so-called "introductory" books on Karl Barth are very, very difficult to read. Guretzki's Karl Barth is a book that I feel comfortable giving to a family member, friend or enemy that does a good job introducing Barth in layman's terms. The book is about 200 pages and it is well written with lots of pictures and charts, making it an accessible page turner. There's no shortage of books on Karl Barth, but within that spectrum, there's a big gap that needs to be filled with Barth 1-0-1 books (like this one) that do not require a Ph.D. to understand, and Guretzki's book is an excellent leap into that void.
A Hitchhiker's Guide to Karl Barth
Guretzki's An Explorer's Guide to Karl Barth is like a travel guide book to Karl Barth. Guretzki introduces his book as follows:
Indeed, my primary objective in writing this book is to provide a guide—a handbook of sorts—explicitly designed to help new explorers of Karl Barth to get quickly acclimatized to his thought. Because I've aimed this book at Barth beginners, I've focused less on the technical debates scholars are having (although I do mention a few of those along the way) . . .
Alongside the primary objective of creating an introductory-level book on Barth, I've tried to keep the prose light, tried to inject some occasional humor (though you will have to be the judge of whether there's anything humorous at all in this book-my teenagers groan at my "dad jokes," so I won't be too hurt if you groan, too), and tried to make the book as user friendly as possible.
Throughout this project, I've kept the image of an "explorer's guide" in mind. I find the metaphor helpful because of the way a good guide gives the traveler only enough information needed to enjoy the sights. Any guide book that has vacationers spending more time reading it rather than enjoying the scenery is, in my mind, not a good guide. 
The guide book format is the strength of this book, because it allows so much different content to be presented in a easy reference format, yet it is still readable from cover to cover, making it a very captivating book that most people can read it entirely in a few sessions.
Each chapter is a different format, making it hard to stop reading at the end of a chapter, because I wanted to see what was next: for instance, one chapter is a biographical sketch, another is a FAQ, and another is a glossary, and it has one that is an overview of the Church Dogmatics, and another with a three-track Barth reading plans. The book also resembles a guidebook by including inline boxes throughout the book containing "Explorer's Tips", "Explore Further" information, "Fun Facts", quotes and references. I particularly appreciated the tips where Guretzki explains how to pronounce difficult names and terms like "Pryzwara" (pronounced, "Shah-VAIR-ah") 
FUN FACT: Barth sounds like "Barth" (as in Simpson), not like "Darth" (as in Vader). Avoid embarrassment and just imagine Karl Barth going to work on Bart Simpson's skateboard and you'll never go wrong. 
Another strength of the book is that is summarizes information in lots of helpful charts; for instance, the chart on page 137 contains a handy list of Barth's Bible commentary, and another chart contained a summary of the Church Dogmatics, Vol 4 (CD IV). The book has lots of other helpful features, such as the pictures of Barth relics, including a Karl Barth stamp, an autographed book by Barth, Barth's desk and the "white-whale" original edition of the Church Dogmatics (Kirchliche Dogmatik); also, each chapter ends with a recommended reading list for further information; and too many other features to list.
I've selected two quotations from An Explorer's Guide to Karl Barth to provide a taste of its content. I really enjoyed the Frequently Asked Questions chapter, and the inclusion of a glossary chapter in the book. I've selected quotations from these chapters to taste of Guretzki's book (but keep in mind, due to the guidebook format, each chapter's content is quite different.)
The FAQ chapter is one of the best chapters because Guretzki's questions are ones I've encountered (or had myself), and he does a good job answering each in a way that is concise, yet still addresses the question honestly without evading the controversy.
[Question:] While we are on the matter of Charlotte von Kirschbaum, I've also heard that she and Karl Barth had at best, an inappropriate, and at worst, and adulterous, relationship. . . .
[Answer:] Those who have examined the history of Karl and Charlotte's relationship have come to differing interpretations about what really took place between them. I can't claim to have enough insight to take either side here, but it is almost certain that there was some level of intimate inappropriateness, even if they (and we don't know for sure) never were involved sexually.
What we do know for certain is the following: (1) Karl and his wife Nelly stayed together for life; (2) there was undoubtedly a degree of marital tension in the household with Charlotte present; (3) Karl and Nelly reconciled in their later years; (4) Karl and Nelly together visited Charlotte in a nursing home in her final years; (5) Karl, Nelly, and Charlotte are all buried together, with Nelly's approval, in the same family plot; and (6) household and living arrangements in Swiss Germany in the early to mid-twentieth century were very likely different than ours, so reading back our expectations of what was and was not appropriate is very likely problematics. . . . 
I'm a big fan of concise theological dictionaries, so I appreciated that he included a glossary chapter. The following entry on Rudolf Bultmann was one of my favorite entries (and the one on Emil Brunner is good as well.)
Bultmann, Rudolf (1884-1976)
Bultmann was a German Lutheran professor of New Testament Theology who worked at the University of Marburg from 1921 to 1951. Barth and Bultmann had both been part of the Confessing Church's resistance to Nazi socialism in the 1930s. Bultmann was in significant dialogue with the existentialist philosopher Martin Heidegger, and though he was influenced by Heidegger's categories, he insisted that he was not wholly captive to existentialist categories. Although there are only thirty-eight entries to Bultmann CD's index volume, Barth himself admitted at the outset of volume IV that "I have found myself in an intense, although for the most part quiet, debate with Rudolf Bultmann. His name is not mentioned often. But his subject is always present." Barth held Bultmann in high regard for his insights but found he simply could not follow Bultmann's method of demythologizing as Barth understood it, and Barth (as was typical for him) tended to highlight the sharp differences he saw between them. Nevertheless, Barth acknowledges and uses many of Bultmann's own exegetical insights, especially in various places within the small-print sections. 
The book achieves Guretzki's goal to be an "explorer's guide" to Karl Barth, and the outline of the book is excellent, but I was disappointed with a few elements in this wonderful book. Guretzki's program for his Karl Barth is brilliant, yet the execution of that program at a few places had room for improvement.
My first critique is that the particulars of some chapters could use another revision. For instance, Guretzki's idea to include a "Glossary of Concepts and People" is a brilliant idea, but he could have chosen better entries, made the entries far more concise, and included many more terms. The worst example is his entry on "dialectic" that spans nine pages (and Guretzky admits that it is "an essay masquerading as a glossary entry")—which is excessive considering there are only about 25 entries total! The selection of terms was odd too, with notable absences, such as on "resurrection", "atonement", "logos asarkos" (especially since "logos asarkos" was given a full page note on page 115), and "analogia entis" wasn't its own bold keyword, etc. (I'm nitpicking because Guretzki had published "The Pocket Dictionary of Theological Terms" with Stanley Grenz—so my expectations may be too high.)
My second critique is that Guretzki's book doesn't compel me to believe that Karl Barth is the answer for today. A good guide book should convince me to want to go to the destinations it describes, and that I should invest the money to commit to this trip rather than others. Guretzki's book provides an excellent starting point, but doesn't leave me convinced that I should read Barth, rather than other theologians.
For instance, Guretzki discourages using the Church Dogmatics in preaching, and this disappointed me because this is a book that I'd like to recommend to preachers to help their preaching! In an odd section, Guretzki concludes that the Church Dogmatics should not be used in the Church, and that preachers should restrict reading Barth to their private study, and not publicly preach the Church Dogmatics on the Lord's Day (i.e. Monday through Saturday):
"Quotations from Barth's Church Dogmatics should be rare in a sermons. That advice may come as a surprise, coming as it is from someone who so appreciates his work. But the practical reality is, most people (even if not all) in the pew really don't care about Karl Barth. And Karl Barth himself probably would be embarrassed to know he is sometimes quoted extensively. Instead, I recommend that Barth quotations are rare, and when he is cited, we should stick to one of his more memorable turns of phrases rather than trying to read a lengthy section that most hearers will likely be unable to digest.
Remember that responsible use of the Church Dogmatics is meant to help you clarify what is being preached against the Scriptures and the voices from the past, but it is not necessarily meant to be a source for filling out a sermon, nor for gaining intellectual kudos from the more academically oriented in your congregation. In short, the Church Dogmatics is best used from Monday to Saturday but should be safely stowed on Sunday morning!" 
Guretzki elsewhere praises the Church Dogmatic's Index volume (which includes a "preacher's aid" and lectionary reading list), and Guretzky even explains how to use the index to navigate the Church Dogmatics. Guretzki is a bit inconsistent on this point, because he encourages reading Karl Barth in groups, and even explains how to organize a weekly Karl Barth discussion group. Discouraging the use of Karl Barth from preaching, was reduces the momentum of this book, in my opinion. However, I believe this section on preaching could have been revised to encourage the use of Karl Barth in preaching (rather than discourage).
Prof. David Guretzki is a qualified reader of Karl Barth, with a Ph.D. on Karl Barth from McGill University, and dean of Briercrest seminary. If you've never heard of Karl Barth, or you want to introduce someone to Karl Barth in layman's terms, then An Explorer's Guide to Karl Barth may be the book for you! Guretzki has written a captivating page-turner, that is both accessible and informative. There is an endless list of Karl Barth books available that could be stacked into a great wall, but there are few that provide an adequate introduction to Karl Barth in layman's terms. Guretzki's guide book format makes An Explorer's Guide to Karl Barth an engaging introduction to Karl Barth, that is a fun and easy read, yet covers significant ground. Despite having a few criticisms, I enjoyed reading this short book, and believe it fills a hole in the great wall of Barth books, and is an excellent first step in the thousand mile journey through the world of Karl Barth.
[^1] Guretzki, David. Introduction. An Explorer's Guide to Karl Barth. Downers Grove, IL: IVP Academic, an Imprint of InterVarsity, 2016.xi-xii. Print.
[^2] Ibid. 117.
[^3] Ibid. 25.
[^4] Ibid. 29-30. [The formatting of this quotation has been slightly altered for readability.]
[^5] Ibid. 55-56.
[^6] Ibid. 163-164.
Disclosure of Material Connection: I received these book free from IVP Academic Press. I was not required to write a positive review. The opinions I have expressed are my own. I am disclosing this in accordance with the Federal Trade Commission’s 16 CFR, Part 255 : "Guides Concerning the Use of Endorsements and Testimonials in Advertising."