Different people learn best in different ways. Some people can get away with just reading the book. Others need to do some examples.
My trick is to read the book, make my own notes of what it says, then do some examples AND mark my work. There's absolutely no point doing example questions if you don't know how well you are doing.
That works for me anyway. You'll have to work out how you learn best.
When you are doing examples, you'll normally be given a question and then a worked answer (most good textbooks have these). Do the question yourself before looking at the answer, so you get practice at actually doing it yourself. A lot of people will just read the worked answer but not learn anything. Then do the questions at the end of the chapter and see how well you do.