I just finished a couple of great books: Christian Beliefs: Twenty Basics Every Christian Should Know by Wayne Grudem and Basic Christianity by John R.W. Stott.
If I had to choose one of these books over the other, I think it would be Christian Beliefs. It follows the same major topics as most full-blown theology texts, and, in fact, is a condensation of Grudem’s 528 page Bible Doctrine, which is itself a condensation of Grudem’s 1,296 page Systematic Theology. As such, there is a wealth of information packed into this svelte volume. I especially found the Westminster Catechism, the Chicago Statement of Biblical Inerrancy, and the ancient Christian creeds in the back of the book to be a nice touch. Grudem also provides a list of roughly 45 books for additional study from a variety of perspectives. I can’t think of a better, more easily digestible introduction to Christian theology than this book, and have already recommended it to several friends and others who have inquired about what I believe.