But if one needs to understand what they are doing, and not just copy the exercise,
the basic examples in this site are better I believe.
If you really want to understand what is going on, you're going to need to do a lot of studying, and more than a bit of math (nothing too tricky, though - mostly basic algebra).
Two books that I like to recommend are:
Schultz's "Grob's Basic Electronics"
Horowitz's "The Art of Electronics"
Both books are essentially "EE101" level material; I'm more familiar with "Grob's Basic Electronics" - it essentially starts out with "what is an electron", then to mainly passives - voltage, current, and resistors, Ohm's law, Kirchhoff's circuit laws, etc; then on to semiconductors (diodes and transistors), and so forth. By the end, you are getting into digital design and whatnot.
Both books are textbooks, and have a hefty price - expect to spend over $100.00 USD for each, if you get the latest edition. That said, you don't need the latest edition - instead, get a previous edition, and you'll spend much less.
In addition, you might also want to look into some of what Forrest M. Mims III has published over the years.
Particularly his "Engineer's Mini Notebooks" series, which were once published through Radio Shack, back when they were a real electronics parts outlet. They present a lot of electronics material in an approachable way; all of these books should be a part of your library if you want to really understand things.