Books

there are so many different problems out there that you won't be exposed to them all. books will be able to give you an idea of what to do with the most common problems, but you will probably mostly find books that teach you troubleshooting methods.
since every environment (workplace, school computer lab, etc.) is different, you will be exposed to different problems in different settings.

my advice to you is that you will probably get more help from the people that you work with, since they've been exposed to the environment long enough to know what problems there are, and what to do about them. no book will tell you about the iidiosyncrasies of whatever particular environment you end up in. any new problems you encounter will require logical troubleshooting and resources such as TechNet.

so basically, my belief is that you won't learn as much from a book as you will from other people. TechNet will help you with quite a few problems, but you have to look for the right things.....

good luck!

While I agree with the answer above, I do recommend a few books that contain information that is invaluable. The Winn L. Rosch Hardware Bible I consider one of the best reference books on the market for PC problems. On the Windows side it's not quite as clear. There are a number of books that are pretty good but nothing that jumps out at you and screams 'I'm GREAT!'

As for on-the-job-training, there will always be a little OJT. Learning new equipment, new operating systems, applications,interoperability, configuration, are just some of the basics you have to contend with. When I am faced with a new piece of hardware/software I look for a book that covers that covers specifics of what I am wanting to learn. I relax in the bookstore for a while, read part of the book and determine if it's thorough enough. I buy it and READ it. Books on the shelf collect dust, and the knowledge never makes it to you head.

Keep reading the questions here at TR and read what you can to try and understand as much as possible. It seems insurmountable for now, but it does get easier.

If you want more information on books I recommend and the like feel free to drop me a note. Good luck with the education!