Just finished reading "How to Write Science Fiction and Fantasy" by Orson Scott Card. I am not sure what makes him such an expert. He's only written about a million short stories and half a million novels. All are fantastic (at least all that I have read - let me recommend the Ender saga and The Tales of Alvin Maker right now). He has also only accumulated 16,000 awards, including multiple Hugos, Nebulas and Locus Fantasy Awards.
Yes, I realize my numbers are exaggerated. That is hyperbole meant to illustrate that Card is awesome and well suited to give advice.
Now, onto the book.
Anyone wanting to write Science Fiction or Fantasy should absolutely read this book. For the cost of a paperback, you get to spend a few hours with a noted expert in the field.
It raised some great points, gives good advice and certainly provides a lot to think about regarding what separates Science Fiction from Fantasy. The two overlap more than you might think and I find I prefer Card's term "Speculative Fiction" which he uses quite a bit.
What I really like about the book is that despite holding some pretty strong (and dwell publicized) religious and political beliefs, Card does not use the book as a platform for that stuff.
This book is about writing. It is easy to read. it is conversational. It is helpful and insightful.
So go get it.