I'll be brief with this review, as there isn't really much to say. There's mixed opinion regarding CGP's books, but I have always found them very useful. Although the colloquial and informal language can get in the way occasionly, they are packed with all you need to know to pass your exams. As a Year 11 student who has recently completed his mock exams, I can testify to just how useful revision guides like these are!
The CGP Higher Maths is no exception; it covers all the topics that you need to know for the exam (and there is quite a lot of them), in enough detail to get you through the exam, but not in so much detail as to confuse you and put you off revising.
For those who are studying on the Edexcel course, the textbooks provided, I find, are nowhere near as helpful. Useful for practise questions, maybe, but this book is unrivaled at making the info easy to understand. However, CGP also offer workbooks containing exam-based questions that go perfectly with the revision guide (GCSE Maths Workbook (including Answers) - Higher
One small point: It says on the book that the guide is the 'new two-tier specification'. This was for when the new maths syllabus was adopted. It now reads on the book "For the 2010 and 2011 examinations only". Now, I must slightly disagree with this point. While subjects like science, geography and english would have syllabi that change a great deal when revised, and would therefore require new revision guides to reflect the changes, maths is not a subject that is likely to change so drastically. The information within is as relevent now as it will ever be, and while the syllabus might start to cover topics slightly differently, the basic information within this book will still be useful, so I would still hand this guide down to younger generations, and would not feel too disadvantaged to be using an older guide myself.
Overall, this book is a great tool for those who are preparing for a GCSE Maths examination, with easy-to-understand wording and diagrams to make revising a little less like revising!