High school math books recommendations I'm in last middle school year and want to learn High School maths in depth — I want to grasp the behind the scenes and learn proofs. What are good books to self study HS maths this way? In what order should I study? 

I add to the answer of Chris a very nice book in English language. I have discovered this morning that some examples are taken from my textbook in italian language.
The name of the book it is the necklace of JAMES STEWART 
Here there is a preview of Algebra: https://www.stewartcalculus.com/data/CALCULUS_8E_ET/upfiles/6et_reviewofalgebra.pdf 
