Oxford University Press has a great idea in its A Very Short Introduction series. Written by experts in subjects ranging from Ancient Philosophy to the Spanish Civil War, each volume provides a concise introduction to a wide range of topics in history, philosophy, religion, science, and the humanities. The books are approximate 6.8" x 4.4" with a page count of around 150. If you want a quick way into a new subject, this is a great choice.
In particular, if you want access into the life and theology of the Apostle Paul by one of the premier Pauline scholars without wading through interminable discussions about what scholar said "this or that," you can do no better than the volume by E.P. Sanders. This is not Paul for Dummies; it is thoughtful, challenging, clearly written, and amazingly brief. You really should consider this one for your library.