If you are looking for a book, Classroom in a book from Pearson eduction is the good book to start with, along with AE Apprentice from Trish & Chris mayer.
If you are completly new to AE, and wanna watch beginner tutorials, you can check www.videocopilot.com they have a "Basic training" that is aimed to begginers.
I second After Effects Apprentice - 2nd edition. Chris and Trish Meyer know their stuff!
This book provides a very clear and consise way to learn After Effects - in an easy to read (not dummied down) presentation.
Also, check out the lynda.com training that Chris and Trish have done as well. www.lynda.com