Scott McCloud, creator of Zot!, produced an important groud-breaking book some years ago, entitled Understanding Comics. That book could serve as the textbook for the first semester in a course on creating comics (be it daily strips, monthly books, or graphic novels). This book would be the textbook for the second semester – where you are taken into greater detail the crucial matters for creating an effective piece of sequential art/storytelling.
Although McCloud is himself primarily an artist, and much of Making Comics focuses on the visual aspect of the medium, this book should be studied by writers as well. The more the comic book writer understands the considerations an artist brings to the collaboration, the better the writer will construct the story to serve those considerations. Writers often focus on the story in their head, seeing it rather like a movie, where the scenes are in constant motion.
But artists have to capture a specific moment. Or capture an image that looks like a specific moment, but really implies the forward motion of time within its frame. (For a better understanding of that subtlety, do read Understanding Comics.) The size of the panel frame, the placement of that frame, whether or not to have the contents of the panel break out of the frame – these are all considerations the artist might be dealing with, but which might never cross the brainpan of the writer. And yet, if writers were much more conscious of the considerations of the artist, and the problems the artist has to address, they would probably deliver scripts that are tighter, and more inspiring to the artist who has to render them.
Certainly this book is a must for the aspiring comic book artist. But I also think it is necessary for the comic book writer.