"He ended up developing an important new epistemological framework that is not only excellent from an academic/technical standpoint, but which provided a general proof that a belief in Christianity is not necessarily irrational."
Yes. An excellent book, and one that all atheists should read, if they haven't already.
A belief in Christianity isn't "necessarily" irrational, to be sure. Many very intelligent people believe in it. A nonbelief in deities and other supernatural entities is also not necessarily irrational. Many intelligent people disbelieve.
Bartley is an excellent, if somewhat dry, read. I highly recommend the book.
Two questions for you, if I may. Have you ever believed? If so, what made you stop?