I just finished reading The Art of Game Design: A Book of Lenses, by Jesse Schell, and it is now one of my favorite books about learning development. (Yes, I do realize that it’s not even officially a book about learning development.)
Whether you are starting from the viewpoint that games and simulations can in themselves be powerful learning, or you are just looking for ways of crafting more engaging, user-focused learning, this book is full of useful perspectives (lenses!) with questions to ask yourself during the development process.
Schell does directly (and briefly) address education as games (and games as education) towards the end of the book. However, from the beginning, by applying a mental lens of my own (the lens of turning everything into learning?), I found 92.47% of the entire book relevant to crafting engaging learning experiences: think problem statements, prototyping, puzzles, user interface design, interest curves, projection, storytelling, aesthetics, and teamwork. The other 7.53%? Still interesting stuff. Go read it.