We have recently had inquiries from several people who were interested in creating books that were community projects involving multiple contributors. Here's the advice we've given these people.
We have met a number of people like you who had great ideas for community book projects, but they never seem to get them off the ground. Why is that? Here are the conclusions we have drawn:
1. You cannot ask non-writers to write. Imagine this: I am not very athletic, yet each year when I visit my uncle he wants me to play golf with him. Golf! That takes years to learn how to play well. If I attempt it, I know I will fail, so I politely refuse. The same applies to writing. It may be your beloved hobby, but to others it is as specialized as golf, a game they do not play. The solution? Ask for their knowledge and stories, but don't ask them to write. Plan to interview these contributors with a digital recorder, just as journalists have done to get the story for many years.
2. The rewards are not clear, or are not powerful enough. It is human nature to ask, What's in it for me? Too often you are the only one who benefits, and yet you want something, either time or effort, for nothing in return. The solution? Create a reward. If you are doing this as a for-profit venture, pay for each story. Non profit? Sometimes even a token payment, such as a gift card for the bookstore, or perhaps a donation to their favorite charity in their name, will make it worth their while. Often, simply offering to get together for a cup of coffee is a good enough "social reward" - people love to get out of the house, and you promise to make it fun for them. The promise of seeing their story in the finished book, however, does not seem to be an incentive, as it is too abstract, at least until the book is actually finished. At that time, they may be very interested in purchasing the book, or receiving a free copy as thanks for contributing.
3. The scope of the project is unknown. Too often, the person who wants to do the community book has "a great idea" but no plans beyond gathering the stories. In their enthusiasm, they pitch the idea poorly to others, who are not impressed. These contributors feel they are being drafted, and they doubt the project will succeed, perhaps rightly so. If the author does not prove that she/he has a good plan, why should they get involved? The solution: Make a plan, and pitch the plan effectively. They will want to know who the other contributors are, and how many stories are going into the book. They will want to know about your plan for organizing the book, your schedule for completing it, and how you intend to publish and distribute it. The money issue must be addressed: are you making a profit, and if so, will they be compensated? In addition to all the information about the book as a whole, they will need to know what you want from them in particular. Give definite guidelines for the length and content of the story. It is very reassuring to hear that there are limits, such as "I just want to record you telling your story for 15 minutes."
4. Relationships matter more than you imagine. They say that all transactions take place in a social context. When people listen to your book project proposal, they will consider their relationship with you before they decide on their interest in your book. Friendships have a loyalty factor, as in "please do this as a favor for me, because you are my friend". Acquaintances do not have any such obligation. They will listen to your proposal, and they will use their reason to gauge the value of the exchange; how much effort will this take on their part, and and how important their contributions are to your plans. That is why it is important that your sources like you, and want to help you, on a personal level. The contributors must have a "good feeling" about the author and the project for it to succeed.
Ultimately, I think that authors who want to do such a book have to take full responsibility for it. They need to accept the role of project manager, as well as author, and they need to be realistic about the relatively small part that others will play. When you ask others to contribute to a book, they will respect your efforts more if they know you have already shouldered the greatest share of the work, and expect relatively little of them.