(Sorry for my bad English.) I've been reading severous QM textbooks that people say are good to learn QM: Sakurai, Shankar, Thankappan. I start reading and understand things in principle, but then I dont get anymore. The only book I think really helped me was QM by McIntyre but it goes not deep in the subject. So is it hard for one person self learn QM, are those books not good enough for self-learning or am I retarded?