When we first got our trailer we got a bunch of RV-related books that, in one way or another, piqued our interest. Completely filled up a milk crate that sits on the back seat floor in easy reach on the hump whenever we travel. Over the years we've kept that "library" up to date as new editions were published.
For the Milk Crate Police: No idea who stole it (if it was). Bought a bunch of them at a flea market decades ago, stamped with the label of our home town long-out-of-business dairy.