Here are a few of the free resources I've used to both learn electrical / electronic concepts in general, as well as those specific to solar. This is not the 'easy' way by any means. But it can provide a depth of knowledge one book alone may not provide:
1) The Navy Electricity and Electronics Series (NEETS)
Navy Electricity and Electronics Training Series, A free self-study electronics course
2) The national electric code:
https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=7
3) Inverter documentation (Just one here, for example purposes, but it's amazing just how much good info is provided by quality inverter manufacturers. Sadly most people don't bother to read their own product manuals, much less research others):
http://www.samlexamerica.com/documen...24-0515-R1.pdf
4) Here's an excellent worksheet that you can really use as written to design a workable system. Just research the 'whys' of the stuff you don't understand (note: it assumes parallel panels even where series or parallel series combos may be better. Same with battery banks. So it's not perfect or iron-clad, but it's pretty darned close).
http://www.dnr.louisiana.gov/assets/...zing_Guide.pdf
5) A couple forums specific to solar which provide excellent info (Note: The second link is a subsection specific to RV/mobile. I suggest you read the stickies. Good stuff there.
https://forum.solar-electric.com/categories
https://www.solarpaneltalk.com/forum...or-camping-etc
6) Great resource on battery options and chemistry in general:
https://batteryuniversity.com/
7) Any manual for any of the main components of a solar system. Those main components being: panels, solar charge controllers, inverters, batteries.
I could go on, but that's a good start. But again, it's not the fast track.