Basically, watch the Longmen special. Two books on inequality are particularly good. In fact, there are many basic studies in high school, which are of little use to junior high school.

The Golden Key Series of Orsay Classic Problem Solving: This book of junior high school mathematics is very good, and it has benefited a lot from careful reading.

Extension, algebraic direction strongly recommends the lecture of algebra deformation high school mathematics competition.

Look at Tian and Shen Wenxuan's "Geometry in Circle, Triangle and Geometric Direction" and other books.

Feng Yuefeng's book "Argument and Structure towards Integration"

Looking at the Olympiad series comprehensively, the books in junior high school are all good.

You can also see the course of Olympic Mathematics in an all-round way.

If you are interested in computer mathematics, you can also read Liu Rujia's book Algorithm Art and Information Blood Competition.

Gartner's "Concrete Mathematics" and "Fundamentals of Computer Mathematics"

Junior high school students can certainly understand and really understand these two books. In high school, it was no problem to win the second prize in the city. No, many of my classmates won the first prize in computer science and the first prize in mathematics.