Quite a few times on a Canyon backpack I have taken a paperback copy of Colin Fletcher's The Man Who Walked Through Time with me on a Canyon hike. I have read this book at least 10 times since I was young. Some like this book, some don't. Old Colin is quite a character. He tries to teach geology while hiking the Canyon, and ruminates on numerous other things as well. He looks for a kind of epiphanic experience whereby he can sort of picture the millenia of the Earth as he is hiking. Not sure he achieves it, but it is kind of fun to read, anyway. It has definitely become a classic of Canyon literature. Sometimes I am just scrounging in my bookcase for a smallish paperback to bring, and I grab that one. It is fun to be out there and realize you are camping in the exact same spot where Colin camped in 1961. He hiked from one end of the Canyon to the other without topping over the Rim. He placed food caches and arranged for airdrops. The whole thing took a couple of months. It was helped greatly by the fact that the water in the river was very low because they had just started filling up Lake Powell. So there were places he could walk along the river, or safely take an air mattress, which are not available today.
One thing I can't do is read poetry, the Bible or anything else deeply spiritual and inspiring while I am backpacking. I think this is because so many times I have been "told" that that is the only kind of book to bring, or you will just miss out on something or other that is very important (to the people who preach that stuff). Most of the time, I take along a murder mystery!