I absolutely loved this book. It is one of the most amazing love stories I've ever read, because they're such intellectual equals to start with. They don't just fall in love with each other, they want to fall in love with all the things that interest and appeal to the other. It gives you hope in the power of unconditional love.
And the second half is even more powerful and profound, when they move to Oxford and meet C.S. Lewis, the wife becomes a Christian and the husband struggles with his human jealousy of her new spiritual priorities, his own skepticism, and the battle between heart and head. It also includes a few letters from C.S. Lewis in the midst of this internal battle, patiently answering his questions and supporting him even in his reluctance to believe. It is a fascinating and heart-warming (and sometimes heart-wrenching) story of what true love really means.