Giving up on Gilead by Marilynne Robinson
(Added two hours later) It turns out I couldn't leave it there after all. Something made me pick it up again - after all, there were only a hundred pages left! I decided to just finish the book, and am glad that I did so because those last hundred pages made all that had gone before make sense. It had to build slowly to make the ending so very moving. I suppose it was about the power of forgiveness on the forgiver.