DISCLAIMER: I'm not promoting these books or websites, just passing along what I hope is helpful information. I make no profit on any of them, nor do I guarantee they will help you as much as they helped me. The links were valid when I created this page. If one's broken, please let me know.
This book helped me better understanding plotting. It taught me the three act, 15-beat structure to shape a story. While reading it, I substituted "novel" for "screenplay" and the information made perfect sense.
The Writer's Journey: Mythic Structure for Writers by Christopher Vogler
As much as Save the Cat helped me, The Writer's Journey made everything much clearer. It breaks down each beat into parts and explains how to use them to make your writing better. This book has become my primary writing guide. I keep a copy of it at my desk at all times.
How to Write a Damn Good Mystery by James N. Frey
This book helped me to better understand outlining and pre-planning a plot.
Self-EditingThe Book on Writing: The Ultimate Guide to Writing Well by Paula LaRocque
(Disclaimer: I know this author personally) but that doesn't lessen the impact of the book. Slanted more toward non-fiction writers, the book still gives novelist some profound instruction on writing clean prose.
Thanks, But This Isn't For Us: A (Sort of) Compassionate Guide to Why Your Writing is Being Rejected by Jessica Page Morrell
This one kicked me in the gut with its blunt honesty, but I found myself repeatedly wondering: "I don't do that, do I?"
Self-Editing for Fiction Writers: How to Edit Yourself into Print by Renni Browne and Dave KingI have met an endless number of fellow writers who rave about this book. I found it helpful, but not worth raving about. However, I include it, because the information is beneficial.
World BuildingThe Writer's Guide to Creating a Science Fiction Universe by George Ochoa and Jeffrey Osier
I stumbled across this one and have found it to be a refreshing how-to book that not only educates but also illuminates. Worth reading if you write SF&F.
Preditors & Editors
This website is an invaluable resource that helps writers sort out the con-artists from the legitimate literary agents. While the webpage is a little old fashioned and sometimes difficult to navigate, the information it contains is priceless.
A great source for markets for your work. Yes, it's for us SF&F writers. Sorry, I can't help with other genres.