Best ACT Math prep book for improving low scores?

I'm worried about my ACT math score because I've been getting 17s and 18s on practice tests. I really would like to raise it up to a 25. Which review book is the best option for me?

I'd recommend McGraw Hill's Top 50 Skills for ACT Math for the best advice on improving your math score. It has detailed explanations of 50 critical concepts you need to know to do well on ACT Math. It also includes sample questions and walks you through the solutions step-by-step, so I think it's a good choice for someone starting out with a lower score. You should also consider getting the official red book so you'll have access to more practice questions as you review. You can look at this article for more details on the content of these review books: