At times intriguing and at times a little tedious, The Most Reluctant Convert: C.S. Lewis's Journey to Faith by David C. Downing traces the great 20th century Christian apologist's spiritual journey from Christianity to a variety of philosophies back again to Christianity. (If it were Tolkien instead of Lewis, There and Back Again would be a good subtitle. lol) The author has obviously done his homework and is very well-versed in all things Lewis. Downing relies heavily on Surprised by Joy, Lewis's memoirs written in his 50's, but he also draws on Lewis's other writings, other authors' writings about Lewis, and also on books that Lewis read and which influenced his thinking and spiritual development (which is where the tedium comes in from time to time *wink*).
The writing is solid and the research is deep and wide. Downing helps the reader to understand Lewis's thought processes and how he ended up exactly where he started ~ at Christianity, though a more robust and thoughtful Christianity than he had held as a boy (unsurprisingly). He portrays Lewis as a brilliant though fallible man and gives insight into the first half of Lewis's life leading up to his conversion to Christ, which is an interesting episode all by itself. If you value the work and influence of C.S. Lewis, then this book will be of interest to you.