So what does make a GREAT accessible book? This list from SET-BC helps us answer that question:
1. Consistent in appearance.
2. Graphics are aligned.
3. Text is true to original; clear and large enough to read easily.
4. Sound recording is clear and has no background noise.
5. Sound recording is activated automatically.
6. Books open quickly.
7. Books open as a PowerPoint Player.
Here's a link to the original document, it includes how-to's on how to accomplish these steps: