Black gates are excellent decoupling caps, but for other purposes they may not be the best choice.
The Art of Electronics is an excellent reference book, but it is pitched at a level that could be a little hard to digest for a beginner. Many electronic engineers refer to it as "The bible".
A good self-teaching book is Electronic Systems by M. V. Brimicombe. It starts from scratch, and covers all of what you'd learn in an electronics A level and some more.
If you fancy something a bit meatier, Engineering Circuit Analysis by Hayt and Kemmerly covers an awful lot of ground, and teaches how to analyse circuits mathematically.