I want to be able to decide on my own, not copy an example from a book. A math book not only gives examples, it gives you problems to solve on your own.
If you're looking for a textbook approach, pick up a copy of Grob's Basic Electronics. Note: This is an EE101 level electronics textbook, meant for college/university courses. A new edition will cost $100.00+ USD. However, a used edition or an older edition will cost considerably less.
You might also want to look into Forrest M. Mims III's "Engineer's Mini-Notebooks" series - which is a wonderful collection about electronics and various projects (however, all of the books have a "theory and practice" portion, and there are couple of books that detail things like how basic components work, and reading schematics and such).
Lastly - check out this site (especially if you are in the UK or Europe):http://www.kpsec.freeuk.com/