That depends on which one you want to take. If it is cie, one book is enough (economics and business). Mathematics seems to have only the Edexcel exam. Mathematics needs a lot of books. AS has three exams, and it is best to choose core.

Mathematics 1, core

Mathematics 2

,

Statistics 1

This is AS's exam.

Generally, A2 should learn core.

mathematics

3,

Statistics 2,

And mechanics

1. I advise you not to choose mechanics. You can choose.

C4 C3 C2 c 1

S3 S2 s 1

M3 M2 m 1

D 1，D2，D3，