To distribute your book on iBooks, you can work directly with Apple or use one of the Apple-approved aggregators listed below. Aggregators can format, deliver, and help market your book. They can also help you meet the iBooks Store technical requirements and manage your book's metadata.
If you work with an aggregator to distribute your book on iBooks, Apple's contractual and financial relationship is with the aggregator.
Neither Apple nor iTunes makes any guarantees as to the quality of these services.
Information current as of June 18, 2013.