The night after I wrote the long post "Where Do You Get Your Ideas?" I dreamed a much shorter way to begin: using question words can kickstart a book art project.
Who. Who is the book about? Who is the audience?
What. What is the subject? What do you want to show? What do you want to say?
Where. Locate the setting. Use the book structure itself as the place.
When. When does it occur? One hundred years ago? Now? The "now" that happens each time someone views the book? A minute from now? Projecting into the distant future?
Why. Why does this material have to be a book? Why is it important to you?
Which. Be specific, not generic. If you mention a rock, which rock? If you draw a flower, draw a specific flower.
How. How will you reveal the contents? Is the pacing fast? Slow? Are the story, information or images hidden in pockets or behind doors? Presented cumulatively? Shown sequentially? How do you want the reader to feel?
Perhaps it is a shorter way to think about books, but it is still a long process. Start answering and sketching and moving materials around, then allow incubation time!