Making Comics: Storytelling Secrets of Comics, Manga and Graphic Novels by Scott McCloud
This is an intense course on how to make comics, told in...graphic novel format! It is an incredible reference book for those that have ever thought of writing a comic or graphic novel. Even if you aren't interested in creating your own comics, understanding the artform and different practices helps you understand, and appreciate comics even more.
I was so smitten by this book, I have already bought McCloud's other famous work – Understanding Comics. This book is actually #3 in the McCloud's series about Comics.