Check your local library, comic shop, or independent bookstore for these:
Comics and Sequential Art and Graphic Storytelling by Will Eisner – one of the masters of comics explains his inventive approach.
Understanding Comics and Making Comics by Scott McCloud – an essential overviews of comics and how they work.
Comics: Easy as ABC by Ivan Brunetti - fun and smart activities for kids who want to make comics.
On Writing by Stephen King – very practical advice for those who want to become writers or improve their work.
How to Draw Comics the Marvel Way by Stan Lee and John Romita - a bit dated, but some good advice on setting up a traditional studio and workflow. There is a video of it too.
Dynamic Anatomy by Burne Hogarth; good fundamentals of figure drawing.
Freehand Figure Drawing for Illustrators by David H. Ross.
Drawing on the Right Side of the Brain by Betty Edwards.
The Art of Comic Book Inking by Gary Martin and Steve Rude.
Perspective for Comic Book Artists and Extreme Perspective for Comic Book Artists by David Chelsea.
How to Think When You Draw and How to Think When You Write by the Etherington Brothers.
Directing the Story by Francis Glebas - a guide for storyboard artists that is also very useful for cartooning.
The Graphic Artist’s Guild Handbook of Pricing and Ethical Guidelines. Extremely useful for anyone who wants to know what to charge for their artwork and how to conduct oneself as a freelancer, even if you don’t plan on being one.