Yusupov's books (Build up Your Chess and Boost Your Chess) are really interesting, and I'm working with them
However, I find the chess pocket Book (by Lev Alburt) and the How to Reassess your chess Workbook (Silman) complementary
Elo 1350 FIDE
Learning from these three books is time consuming. So here are my (two) question(s) : are the Yusupov books sufficient and are the two other books (tactics and strategy) really useful ?