I first found the Writer's Workshop of Science Fiction and Fantasy at a convention. As soon as I saw some of the names of the contributing authors I knew I had to grab a copy. It has since become one of my favorite books of writing advice.
What makes this collection of essays so different is the focus of each one of the individual pieces. Rather than generic advice like 'show don't tell' there are discussions specific to the world of sci fi and fantasy. Essays about how alien to make your aliens, gender, and worldbuilding all have a home right alongside pieces about the craft of writing, and editor's advice.
There is an essay for just about anyone in this collection. One of my favorites in the collection is "Unbending Gender by Nisi Shawl though every essay has served me well at some point when struggling with a fantastical story.
This collection fits quite nicely against my copy of Stephen King's On Writing and is one of the books I loan out on a regular basis to other writers no matter where they are in their career. If you don't have a copy yet, I suggest you get out there, grab a copy and start diving into the incredible world that opens up in science fiction and fantasy.
You can buy it here or at your local indie bookstore.