[HarryT]

A publishing contract is either "exclusive" - meaning that the publisher has the sole right to distribute the book in a particular country or part of the world - or "non-exclusive", meaning that the author is free to also sell to other publishers (eg Baen always have non-exclusive, world-wide rights on a book). A contract may or may not include eBook publishing rights. In addition, a contract (especially for a new author) may give the publisher "first refusal" on further books from that author for a specified period of time (or a specified number of future books). But in all this, the actual copyright is retained by the author.

Opt-out clauses are very much a matter of the individual contract, but the publisher, for example, may have the right to withdraw from the contract in the event of poor sales.