Over the years, I've acquired dozens of books relating to bicycles and cycling. One of my favorite types ( many of which have been written over the past 130 years) are books by folks who took off on amazing journeys on a bike. All the way around the USA, following the outer borders. All the way around Australia. From New Jersey to New Mexico, on Schwinn Suburbans, with a wife, two teens, and a toddler. Most of their gear in wire baskets. And so on. Makes me think I might try such a thing someday.
Another "genre" are the "Everything You Need to Know About Cycling" books. It is fun to compare a EYNKAC book from 1970 with one from 2005. Thirty years ago, the assumption was that you would be doing long tours, or commuting to jobs or school. Now the assumption seems to be that you are riding to "get fitter", or "get faster"...
Old-time repair manuals are interesting. Many provide detailed instructions on how to take apart and repair a three speed hub. I've never met anyone who dared to do so , but the old-time books assume any 'ol bike owner might want to attempt that feat.