Are For Dummies books good for self-studying geometry and trigonometry?

[McWonald]

I am planning on doing a huge self-studying over geometry and hopefully a little bit a trigonometry session over the summer at my public library. Over at a friends house, I see that he has a book about "algebra 2 for dummies" in his pile of science books and it got me wondering, are the "For Dummies" book series a good way to learn math?

 

[Simon Bridge]

The short answer is "it depends".
What you need is a book designed to be a course rather than as a primer ... or just do one of the courses online.