It's coming up to Christmas so I can ask to have all the books I can't afford from begrudging relatives! I'm really interested (mainly from looking at some of the answers cleo and other fantastic users!) in being able to approach integrals from a variety of different ways and learning how to tackle non-elementary integrals.
I've gone over a lot of the standard techniques in my undergrad and this is just for a hobby, so don't want anything too 'heavy', just great explanations and a lot of questions to tackle. So far I've found Irresistible Integrals: Symbolics, Analysis and Experiments in the Evaluation of Integrals. Many thanks.