I'm looking for a text to help someone who uses GLMs in practice become familiar/comfortable with GAMs. Online or physical textbook would be fine. I am approaching this as a practitioner, so I would prefer practical to theoretical, but I'm confident I have the background to digest a more theoretical text if it happens to be particularly worthwhile.
I also use R, almost exclusively. If you happen to know of some R oriented texts/tutorials that'd be really appreciated.