When I started my GCSE maths syllabus, my brother gave me this book that he had used at school some years previously. It is superb. It starts right at the basics with arithmetic and fractions, percentages and through to algebra, both basic and quite advanced. Logarithms, calculus, trigonometry, matrices, vector and then a section on statistics.
A good portion of the content is no longer in the GCSE syllabus and is now part of the A level syllabus. Make of that what you will.
Some of it may seem dated, for example the chapter on using 'The Electronic Calculator' and the chapter on 'Decimal Currency' features sums with halfpennies in them. There are a few chapters on calculating salaries, simple and compound interest, and investment and bankruptcy which may well be useful in real life, though hasn't been in any syllabus for over 20 years.
Each exercise is preceeded by an example or two and then has rated each question on a scale of difficulty A-D, for example:
"Exercise 2 - Questions 1-4 type A, remainder type B".
All the answers are in the back of the book.
I cannot recommend this book highly enough. It's not all colourful and full of pictures like modern textbooks are, but it is easy to read and isn't impenetrable like some old textbooks as the text is quite well spaced out. If you are starting out in maths or have children starting their GCSE maths, and they're willing to sit and work through this book, they should do excellent in the final exam and if they go on to do A level, they will have a headstart on the rest of the class too.