http://www.cards4magic.co.uk/acatalog/Books.html
whether you are just starting, or are interested in testing the waters with something new - try the above link.
There's the classics for under a tenner, Royal Road and Coin Magic and there's Dear Mr. Fantasy for £24; and a somewhat over-looked little booklet called 202 methods of forcing by Annemann for a couple of quid...
Im a sucker for the old covers too...there's some great ones available...
By the way this site is also very useful for different thumbtips and cheapo gimmicks if you just fancy a little try out...i got a sanada gimmick the other day from there and its surprisingly good...
It's also absolutely superb for all your card needs...im rather partial to the Kems Paisley cards...
Anyway, fill yer boots! more often than not next day delivery in the Uk too...enjoy!