Bundles are a hot new trend for self publishing indie writers these days, and multi-author bundles are a great dea for both readers and author marketing. These anthologies of short stories or novellas give readers more of what they're looking for: great stories in their favorite genre. This strategy also applies to non-fiction where the subject matter is similar. For the authors, they're a great chance to be discovered by many more new readers than they might otherwise find. The rewards for writers can be huge in terms of sales and recognition, but bundles don't come together overnight. It takes a dedicated, organized person to put a bundle together, but the effort could pay off significantly.
The Legal End
When dealing with multiple authors and their works, you'll need to come to an understanding of copyright permissions. Most bundle editors create a boilerplate form for all authors to sign, assigning rights to their work on a limited basis. The editor is allowed to use the work once in the bundle, and then rights revert back to the original author. This protects both parties in case of any disputes.
Money
Hopefully your bundle will be a great seller because it's such a bargain, but what about all that money rolling in? First of all, most successful bundles are set at a minimum price, usually $.99. (can be significantly higher for non-fiction) The idea is to sell as many copies as possible, not to make a lot of profit, because a bundle is mainly an advertising tool for all the contributing writers. Even though the book is cheap, there will be some small royalty payments coming in, and after you pay the editor back for expenses there may be profits. Decide ahead of time what to do with them. Do you want to invest the money in book marketing? Give it to the editor for her time and effort? Donate it to a worthy cause? However the money is to be split, get it in writing before publishing anything.
Organizing
Have the final shape of the book in mind when you start the process. Most anthologies, or bundles, contain ten to twelve short stories a half a dozen novellas or chapters of non-fiction expertise. This brings it up to around 100,000 words, making the book or ebook a significant size and a great value. Define your genre sharply. It's not good enough to simply include romance stories. Make all the stories romances in 18th century Scotland, or dystopian science fiction, or some other small niche. The more specialized the better, when it comes to finding readers.
Where to Find Writers
Most writers who deal with indie publishing are members of multiple writers groups online, Tap into your group memberships to find your contributors. Emphasize that it's a book promotion, not a way to make more money directly. Let them know that they can include back matter into their portion of the bundle, so they can market the rest of their book series, their new audio book, or a list of any other works they want to push. With a large enough group, you may end up having to put out a second or third bundle, just to satisfy all the demand.
Keep the Faith and May the Force be with You!