[AudiomaticApp]

I enjoyed Art of Problem Solving books as a kid. Some of them are online, and you can probably get them second-hand for relatively cheap. They're better at provoking critical thinking than most math textbooks, and favor puzzle-solving and proofs. They're targeted towards K12, but are much more rigorous than most school curriculum, so they should be a good fit if you're currently reviewing GCSE-level math.

https://artofproblemsolving.com/store/online

Each of their courses have an "Are You Ready" quiz. You can take the quiz associated with the textbook you're interested in to see if it's at an appropriate level.

https://artofproblemsolving.com/school/recommendations

[trwhite]

Thank you :)