These days there are a gazillion books on screenplay format, but GN format is pretty hard to find.

I have:
- Eisner's "Comics and Sequential Art" (great for artists, nada on scripts)
- Salisbury's "Writers on Comics Scriptwriting"
- Gertler's "Panel One"

What other books do you recommend?

I'm new to this, and the only ones I've read are Scott McCloud's books.

I'll second the suggestion of Scott McCloud's books for those who both write and draw. Great stuff about things like panel layout, pacing, etc... Amusing and informative, too.

I supervised a comic book writing class one year at MOCCA, and our guest lecturer from Marvel used tips from Story by Robert McGee. I've found that screenwriting books like that one, Save the Cat!, Making A Good Script Great, and Screenplay are just as good as books that focus solely on comics because they focus on how to tell an effective story. Scott McCloud's books are also good though, as is The DC Comics Guide to Pencilling by Klaus Janson.

Yeah I defintely agree with the scott mccloud books but also articles & interveiws with graphic novel writers about what they think about writing etc can be really good. Especially the ones with Grant Morrison, Warren Ellis and Alan More. Their is also just the general books about writing which can help as well.

Can't remember the guys name, but he said if you want to know how to write script, take a comic book, sit down and write the script you see panel by panel, page by page. By the end of the comic book - you know what to do. It works. :]

Anyway, 4 of my faves:

"Animation from Script to Screen" by Shamus Culhane (yip, it's animation, but it still works)

Will Eisner "Graphic Storytelling & Visual Narrative"

"Super Heroes. Joe Kubert's Wonderful World of Comics." (really good script stuff in the last section)

Another I really like is Tom Bancroft's "Creating Characters with Personality."

I'd definitely second Eisner's and McCloud's books for anyone that wants to work in comics in any way - visual storytelling's just as important for writers to think about as it is for artists. Your artists will thank you if you have a good visual understanding of the page!

For formatting stuff, there's no one generally accepted style, but I really like the format Dwayne McDuffie (Milestone Comics, JLA, Deathlok) has examples of on his homepage:
http://homepage.mac.com/dmcduffie/site/X-O_-19_script.html

As far as structuring your script and basic layout of your panels I have yet to find a good "one true way" tutorial. It seems as though every different writer has a different format for their script and some even have different formats depending on who is doing their pencil work. However, as far as everything else is concerned... from character development to pacing to creating story arcs across multiple issues my recommendation would have to be:

Writing for Comics with Peter David

I just finished reading Scott McCloud's book 'Making Comics.' I really enjoyed it. I am also looking forward to reading Eisner's book, but Making Comics seems like a great place to start because there is so much about telling the story and even information about the business of comics.
This Monday, I get to go hear Scott McCloud speak at the Writer'sUA Conference in Seattle. What great timing. It will be more geared towards the use of comics in help, like he did for Google Chrome, but I should still be able to pull some good inforamtion from there and inspiration. Maybe I can even think of a way to get some comic style help into the help I work on.

... I've seen that book, but never bought or read it... I want to, though.

I'm currently re-reading through "Making Comics" by Scott McCloud. It's quite helpful. I was trying to write a comic script for my other story just to get familiar with CeltX before Script Frenzy starts, and I had no idea what I was doing. I think I'll go a bit faster during the actual thing now that I've read some of that book again.

The first information I encountered about writing GN's was in the back of Sandman, Dream Country (I think!) where Neil Gaiman provided a copy of the script for the story Calliope along with notes from the artist & his own notes. That was my first intro to scripts...It was useful to have a copy of the script and then the finished product to compare side by side.

the books by Will Eisner
the books by Scott McCloud
Writers on Comic Scriptwriting volumes I & II
Artists on Comics Art - Mark Salisbury
Come in Alone - Warren Ellis
How to Make Webcomics - Scott Kurtz