Beginning Ubuntu Linux
While I have not actually read the book, some of the people I have suggested 'Moving to Linux: Kiss the Blue Screen of Death Goodbye!' (mainly as it was the only book I have found aimed at the beginner and that i was impressed by the quick flick in the bookstore) as a good place to start have been very impressed
Moving to Linux: Kiss the Blue Screen of Death Goodbye!
By Marcel Gagne
Publisher Addison-Wesley Professional
It even comes with a version of knoppix so people can try before they completely commit to linux which I have to say I think is very important.
I was surprised to find recently when I friend of mine (complete technophobe) was given a knackered laptop that when I put ubuntu on it he was very pleased and gave less trouble than a lot of people found when changing between windows versions