For mathematics: The most important part is the problems. You can actually start at the problems, and read the sections until you can answer the problems. Most people avoid the problems because they take time and require them to actually think about the content (it's painful). So my advice: Pick the problems you find interesting and see if you can find solutions to them from the content of the book and learn that well. That would be the most optimised form of studying mathematics. Note: You do not need solution sets to do this.