Lol how much did you buy them for? I'm thinking of buying a copy of them for myself off the yr 12s at my school- the school offers to buy it for us but it costs 40$ -_-, so trying to get a better deal off the yr 12s, they sell way cheaper.
Wait by topic, do you mean module? Or like, say le chat principle, equilibrium constant and so on, which is like the principle they follow in the success one maths books I think?