One category of books recommended by many is Christian biography. God Made Them Great  by Scottish minister John Tallach is a set of mini-biographies. Two of these people are fairly well known, the others are relatively obscure, but all are “great” servants of God. You can pick and choose from: George Muller (1805-1898), Isobel Kuhn (1901-1957), Billy Bray (1794-1868), David Brainerd (1718-1747), and Robert Annan (1834-1867). The work of each is summarized on the back cover.