Hands down - the most useful books I've found about RVing have been the Owners Manuals. Read the one for your coach first. Know that aside from the walls, the floor and the cabinetry - virtually everything in your coach was manufactured by somebody other than the company that made your coach.
Start looking around to identify the manufacturer's name of everything you can. Then Googling those names to try to download the Owners Manual for every item in your coach. Download 'em and store them on your computer - and then start reading them.
The "big" items are easy (manuals for the appliances, the engine, the transmission, the generator, etc.). But don't overlook the little stuff - like manuals for your awnings, window shades, toilets, etc.
You'll be amazed at how much you'll discover by reading those manuals. Sure, the material is drier than a popcorn fart ... not much of a plot, often poorly translated from the Chinese, Japanese or Korean it was likely written in originally ... BUT, reading those manuals will undoubtedly save you BIG money in the long run and help you get the most satisfaction out of your coach in the long run! There's a treasure trove of information about how to clean, adjust, use and maintain virtually everything in your coach buried in those manuals.
Read 'em once ... then read 'em again. Then pull 'em out and read 'em again every now and then.