I'd never read a collection of letters before. It was an interesting journey. Quite apart from the obvious material regarding the Legendarium, it was fascinating both to read the details of Tolkien's Christian faith and how he slowly fell into the "Get off my lawn" mentality. I also found it interesting to read of his distaste for the Tolkien Society of America (American fandom in particular), and, I think, fandom in general.
I though the glimpse into the man was fascinating, in the end, and for anyone at all interested in the Legendarium at any level, "The Letters" must be required reading. I'm unhappy it took me into I was 57.