Will Eisner is a classic. He's work is an inspiration for many artists.
I recomend Scott MacCloud third book Making Comics. It explains the sequence between pannels very well. It's a very complete step by step tutorial book.
Directing the Story, by Fancis Glebas shows an entire storyboard, storytelling step by step of an animation. The tips and advices are great to use in webcomics too. It's a great