Cambridge International AS & A Level Computer Science Revision Guide

If you are looking for an A* this book is not going to give you one. I find Z-notes way more useful than this book. It is almost as if the author avoids answering the questions in the spec and simply mentions them here.

compared to the course book the information is more summarised and more clear (main parts that you're supposed to learn mentioned in the syllabus are well explained with a lot of worked examples especially in the programming chapters). maybe some parts are explained in a better way in the text book so I would suggest to use both. there are a few past paper questions at the end of each chapter and other exercises in between the chapters. this book would help you to understand the information more clearly, but to prepare for the exam I would suggest to get this and do many past papers!

Good textbook to have, like all text books for A/As level CIE computer science, you have to use multiple, none of them cover quite enough in the right amount of detail to answer all exam questions.