I realised, to my horror, that there was an abject lack of decent A-level maths e-books available for the Kindle, so I set to work putting that right. You have a choice of:
20 Questions on EdExcel Core 1 Maths: a complete overview of the C1 maths course.
20 Questions on EdExcel Core 2 Maths: Logarithms: Everything you need to know about dealing with C2 logs.
20 Questions on EdExcel Core 3 Maths: Trigonometry: All that stuff about $\sin$ and $\cos$ and $\sec$ and what-have-you.
20 Questions on EdExcel Core 4 Maths: Integration: A wide-ranging masterclass, taking you from integrating powers to solving differential equations.