Reddit mentions of Algebra the Easy Way (Easy Way Series)

Algebra the Easy Way is really helpful.

Another book of number puzzles I loved when I was a girl about her age were the Sideways Arithmetic books. They add and subtract words to get another word, and so you have to apply logic to figure out which number each letter represents for it to add up correctly. I learned algebra mostly from the book Algebra the Easy Way. It introduces principles of algebra by having characters in a fantasy story face problems that require them to develop the algebra techniques to solve, and it comes with exercises to practice. There are other books in the series, including one for trigonometry and one for calculus.

For an adult reviewing algebra, you might want to try Algebra the Easy Way. It's published by Barron's and looks like a study outline, but its looks and title are quite deceiving. In fact, it's actually a highly conceptual approach to algebra and does a very good job at explaining what the subject is really about. It even includes a lot of level-appropriate proof-based reasoning. (For example, it includes the famous proof of the irrationality of square root 2.) I read through the first few chapters, and I thought it was quite excellent. The caveat is that I read it from the perspective of a mathematician, not as someone trying to learn anything from the book.

One important thing to remember when you encounter trouble on your highly admirable mission: Mathematical competence comes from a huge amount of practice and repetition. Because of this, hitting the fast-forward button on your mathematical education is bound to have certain limitations. So don't get discouraged. If you hit a brick wall, it's not because you aren't smart enough. You just need more practice!