While there has been hundreds of books written about 12 volt dc power and I own a couple of the popular ones used by rvers.
For a complete overview of this subject it is hard to beat Mark Neweth's two part article. http://bart.ccis.com/home/mnemeth/12volt/12volt.htm While equipment and gadgets change, the basic theory will stay the same.
For solar charging theory and what works (I always like to look at real world working applications from people not trying to sell you anything), try reading what Bob has to say on the subject.
I failed to link to the manuals about my 2025rv meter.
Just to confuse you even more try reading all of Phred's Poop Sheets: