Students are often worried because they find difficult or confusing IELTS questions on the Internet (especially for writing task 2). My advice is: don't trust questions you find on the Internet. They are often written by students who have remembered them wrongly.
You can definitely trust the Cambridge IELTS books. Cambridge makes the IELTS exam, so you know that the questions in those books are 'real'. They are also clearly written, so you will not be confused about what the question is asking you to do.
PS. I promise I'm not paid by Cambridge to advertise their books!!