The Course of Mathematical Olympiad in Senior High School is an old book, with both classic and old topics and innovative development. We should read through the whole book and draw inferences from others.
Personally, I think it is necessary to take the "senior high school mathematics Olympic course"
Mainly, supplemented by the new high school mathematical olympiad guide, the new high school mathematical olympiad practical textbook is a new topic, which is also based on the old one, but basically the same. I think the new one is not as clear-headed and clear-headed as the old one! As long as you can really understand what the questioner means, a book is enough. The key is to think more and think more.
I wish you success in your studies!