At my local church, I've been leaning heavily on Louis Berkhof's "Summary of Christian Dogma." I'd place Berkhof's "Systematic Theology" at the top of my list for one-volume systematic theologies, and this short book is a concentrated summary of that work. If you teach an overview of Reformed Christian Dogma at your local church, then I haven't found a more useful book that Berkhof's Summary of Christian Dogma to use as a basis for that course.
The Summary of Christian Dogma includes the very minimal and necessary verses and summary of each of the Systematic Theological Loci needed to cover the entire Rule of Faith and Full Council of God. It's far superior to Alister McGrath's Introduction to Theology, in my opinion, because even though it omits contemporary theological issues due to its 70yr old age, however, it covers all issues up to its initial inking in concise and precise perfection. 5 stars. It's all online too!