I have loved the idea of Storybird ever since I first heard of it. If you haven't, it's essentially a site where illustrators could contribute a number of images, whatever they liked, and users (mostly kids and students) would get on and write their own stories using those illustrations. That, in and of itself, was a big hit with educators.
Then, Storybird made it possible for you to create printed versions of the stories you made (the illustrators receiving a certain royalty) which was also cool.
Now, the good folk at Storybird are introducing a whole new concept—not just to their site, but to the publishing world in general—longform books.
I happen to be fortunate enough to participate in their initial go of it, and have been working on illustrating a fun YA mystery by Eliza Osborn called "The Mystery of Dogwood Cross."
Four chapters are up now, with more to come!