Other than the multiple PDFs of writing books I sent you via email, there is also "Words for Pictures: The Art and Business of Writing Comics and Graphic Novels" by Brian Michael Bendis (credits include Ultimate Spider-Man, Avengers, Daredevil, Superman).
I recently read it. The book doesn't exactly teaches you how to write nor the basics of storytelling. It provides guides on what to expect when working with editors, writers, and artists, as well as giving knowledge of the business side of the comic industry.
Bendis does have tips on writing, such as:
*I love doing research. It lets me know whether I’m on the right path. So much of my research doesn’t make it to the page, but it makes me feel more confident about my pseudoscience silliness. If the research is boring me, then I know the subject bores me and I should probably move on to something else.
*Ultimately as a creator, there is no off switch. You are taking in things that you experience in your life, and your story and art becomes that laboratory for you to make sense of it. You are processing things that you are interested in and passionate about—childhood traumas, family ordeals, things that make you happy and give you joy, things that make you sad or hurt you. Those are your influences.
*The world is there for you to listen to, observe, and take in. You have to train your brain to not only listen to the conversations in your life, but to recognize how those conversations sound. You need to listen to the music of the world all around you.
*There is a quote from Peter Gabriel that I carry around with me: “Success is a fickle mistress. If you go chasing her, she will ignore you. If you leave her alone and just go about your business, she might come looking for you.”