You can never go wrong with "Card College". This series has 4 volumes. It starts in volume 1 with real basic but important grips and moves and covers in the later volumes pretty difficult sleights. You also get a lot of important theory.
You will hardly find another book with such detailed descriptions of the fine points, common errors and possible variations. You get the life long experience from a professional card magician - one of the best I may add.
And now you can get volume 1 also as ebook. The great benefit here are the 89 embedded video clips which describe every move. This is particularly helpful for someone starting out. The ebook has updated text and illustrations, too, but is otherwise the same as the book: Card College 1 - the ebook
The ebook will be soon reviewed in the big magazines. Michael Close's review should appear in November in Magic and I think the Genii review by Joe M. Turner should not be too far away either. The feedback I received from customers so far is better than I could hope for.
There are of course other good card books available. "The Royal Road to Card Magic" was already mentioned. After Royal Road you could move on to "Expert Card Technique". "Encyclopedia of Card Tricks" doesn't give you any moves but lots of interesting tricks. (These three books are also available in electronic form.)
But again, with Card College you get a modern work which is in my opinion the best and most comprehensive series of books on cards available today.
preserving magic one book at a time.