I'm using this series of OpenStax math books to reteach myself the math I used to know. It's well organized, the coverage is good, and it has plenty of exercises and example, but I hesitate to recommend it because I kept running into examples and exercises where the book gave the wrong solution. I know it sounds like I was probably just doing the math wrong, but I checked several of them on Wolfram Alpha to make sure I wasn't going crazy, and in several cases--maybe once or twice per chapter?--the book was wrong. They definitely need to proofread it more carefully. That said, I felt like I learned what I set out to learn, and of course the price was right.
I relearned a lot and I appreciate that there are many practice examples. I actually found it more useful than khan academy. The videos from KA are nice for a (somewhat) deep dive into a topic, even basic ones which schools never have time to do, but doing lots of examples helps to lock things into memory.