Way back when I bought "Anybody's Bike Book" by Cutherson. It had simple line drawings of all the bicycle components. It's how I learned to work on bikes. About 25 years ago I acquired Zinn's "The Art of Mountain Bike Maintenance." It has the same kind of basic charm. Don't expect it to tell you everything there is to know or even everything that you'll need to know. Part of the fun of working on bikes is figuring it out for yourself when you encounter something that just isn't working quite right.
__________________
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.