Booktype is an open source program for creating ebooks and preparing them for distribution on Kindle and iBooks. Booktype is designed for collaborative use by a group of writers. You can update your books and redistribute them even after your initial publishing date.
To clarify, Booktype is not a service it’s an open source program that you can download and install on your own server. If you have the skills to manage it, Booktype could be a good in-house solution for digital publishing.