Is it beneficial to do one book twice or two book once or repeat the difficult questions from one book. I am asking this in context for preparing for tough competitive exams such as Joint entrance exam advanced (IIT JEE) and International Mathematics Olympiad.
Though I am a student who is self studying, I can phrase this question as if it is asked by a teacher to make this question about Mathematics Educators (and not math student). But will this question be well received? Will this be on-topic? Any suggestions on improving the question?