I'm currently 18 years old and only as of the part year taken a strong interest in maths. I'm working with my school curriculum (UK a-level) and receiving A grades so I am happy with this. However I want to study competition style problems (or problems that are harder than the usual level tested at school). I want to do this for the pleasure required from solving and not for the competitive nature itself.
Having read the previous questions posted, I have seen that the AoPS books/brilliant.org resources seem good to improve problem solving capability. Of which of the AoPS books do I require? I wish to be able to succeed at solving algebra/equality/geometry/factorization style problems.
Is the book by Paul Zeitz (art and craft of problem solving) a good place to start? I feel intimidated by the problems in many papers like the BMO/senior maths challenge and feel it maybe a big jump. Is there a set list of requirements prior to attempting any type of these competition problems?