Here I Stand : A Life of Martin Luther by Roland Bainton is a best selling biography of Martin Luther (amazon). I found a 1955 paperback edition at Half Price Books for a few dollars. My copy has about 300pages and says "Over A Million Sold" on the cover. The first chapter is captivating, and every other page has a wood cut print from the Reformation Era that corresponds to the biography. So its no wonder that this book became a best seller, based on woodcut prints alone.
Bainton tells us about Luther's belief in God Almighty who is the Creator, he would also suggest that Luther believed in sprites and fairies in the forest like other German peasants had those superstitions. Bainton would quote Luther's love for his wife Kate, and then describe Luther as a misogynist who oppressed his wife because he wanted her to stay at home and be a housewife.
Bainton critiqued Martin Luther's theology, suggesting that it was very good but not on par with modern theologians. The entire church has not abandoned the Reformation to follow the German Higher Criticism, especially if you consider how this book was written shortly after World War II.
The biography has amazing prints, and does cover the whole span of Luther's life, so it is valuable to read. Bainton's biography is a helpful and critical assessment of Luther.
(I've attached two wood cut prints by Lucas Cranach the Elder that were employed by the book. The first shows Christ sitting as he washes Peter's feet while everyone is standing, and the second shows the Pope standing, why everyone bows down to him.)