i just finished Earth Power actually, i liked it, flew through it, but i always seem to fly through Cunningham books. the first couple chapters i found very visual [like i could picture everything he was talking about perfectly] once he got into part's two and three, while i still enjoyed it, a lot of the information and rituals weren't very in depth. just a very basic 'this is [insert path] this is the history, this is what it's best used for, and here's 3-5 spells.' lather, rinse, repeat. there's a reference chapter in the back if you need to quickly look up a rune or an herb, really like that, but overall, i wish it was more informative. it does give basic information, if you wish to learn more, find a book diving further into candle magic, or knot magic, or whatever. i got my copy as a Yule gift, if you can find one at your library, or at a used book store, buy a copy. [i think it's on google books]
Wicca: a guide for the solitary practitioner is his most famous book, and although i'm a HUGE Cunningham fan, i'm a little embarrassed to say this one isn't in my collection. been meaning to get a copy for a while now. i'd get a copy, but like i said i love Cunningham, i'd say buy every book of his, even if i found it lacking. from what i've heard from other people, it's a great book, however, it's not a great Wicca guide. [funny since that's the title] his approach to Wicca, and indeed witchcraft, is 'if it feels good, do it.' which on some levels is true, but Wicca does have a few rules. Scott turns around and preaches how it comes down to you to choose what you wish to follow, and this isn't 100% true with Wicca.
A guide for the Solitary practitioner is a pretty good book. I thought it was very helpful. Scott is a very good auther, I'd suggest reading more of his books when you are done with the ones you have.