You've always been a do-it-yourselfer but you do not have experience in all the areas of classic car restoration. You can replace parts, do a tune up, and you've even done some interior work before. Engine rebuilds and body work are something you've never touched but you would like to learn.
The online book stores are overflowing with How To books on all the topics you need to get acquainted with to restore your baby, but there are so many. Which ones do you buy? The list is endless!
It seems a bit basic but the best way to get started would be getting a copy of the factory shop manual. Why the factory shop manual? Because the factory shop manual is going to give you all the details on things you will not find anywhere else. You'll find expanded diagrams of components like doors and window regulators, the suspension system, front end sheet metal, and even the under dash components. You'll need these drawings later. In most cases, after disassembling parts of the car you will not get back to it for 2 or 3 weeks or more. You'll need the exploded diagrams to match the parts together again.
The factory shop manual is going to provide visual references as well. You'll need these when shopping for parts that were missing when you bought the car. If you've never seen them before, how would you know you've found the right part at a swap meet, junk yard, or car show? An added bonus now-a-days is that a lot of shop manuals are available on CD and some of these images can be easily enlarged using a picture manager.
A car specific parts number and casting number guide is invaluable. Why a parts number guide? Well, .. there are a lot of NOS or New Old Stock parts out there and they all have part numbers on them. Let say for example you have an early 60's Chevy and a part you are looking for was reused over 2 model years but changed the following year. The difference between these parts is minor and they will both fit your car. If you know the correct part number you can make the right parts choice.
Maybe you are looking for the correct exhaust manifolds for your car. Over the years the originals cracked and were replaced with something else that "fit". This was common practice during the early years, when your car was someone's daily driver, because they did not care what it looked like. This is where the casting number guide helps you ensure the originality of your ride.
The books you could buy are of great value to you when you really need them. That would depend on what stage of the restoration you are on. Buying a book on sheet metal body panel replacement might not make sense when a casting number guide would be of more use to help you identify those key parts that were missing. An engine rebuilding book would be premature if it meant rebuilding the engine first and then you had to leave it in the corner for 3 years because the car was not ready yet.
If you are lucky enough to find a drivable classic car that just needs some interior work and a new coat of paint, then the books recommended earlier would not be your first choice. Even still, the factory shop manual is not going to be a waste, since that beautiful driver you just bought has reasonably had a few incorrect parts replaced over the years.
With so many books to choose from, take stock of what your classic car needs first. Buying books to put on the shelf does not make sense if the next revised edition has already come out by the time you get around to using it.