You are all set. The approach to your topic is inspired. A firm table of contents has been finalized. Your Book Proposal is great. And you now have a contract with a respected publisher!
But, who is going to do all this writing? You have probably carved out specific chapters that you will write. You may have spoken with some colleagues that like the project and said they would be glad to help out. You have a list of likely people to write other key chapters, but you will need more contributors. How do you go about identifying and asking people to contribute to your book?