Many years ago I was driving a tour bus in Idaho. The bus was full of people from all over the US. I had a tour director who seemed to know many little details about the roads we traveled. I am from Idaho and did not know these facts! I asked him about it, he showed me his copy of "Idaho For the Curious". I soon bought my own book, this book was one I bought for my daughter.
This is not a travel guide in the usual sense--but a boon for history buffs. While campgrounds, hikes, and other attactions are mentioned in passing, the emphasis is on history and sometimes geology of each route covered. It's as interesting an armchair read as it is a companion for the road. As a Montana resident, I wish we had a book like this covering the Treasure State.