Have you read the contract? Do you understand what it means? Because if you don't you may well be signing away the rights to your book forever. Recently some of the largest names in small publishing (Ellora's Cave and Samhain) have gone under. Quite a few smaller publishers have gone the same way. And every time, authors are stuck with not being able to re-publish their books. But it's not just failed businesses. I have friends who bitterly regret signing away their rights to books forever, when their relationship with the publisher went pear-shaped. Most of the circumstances where rights to a book revert to the author, such as the book is out of print, don't pertain to ebooks.
This article gives an insight into why publishers are loathe to return rights.
I have twice been on the wrong end of a failed small publisher. I was fortunate. I was able to regain my rights. I suppose I should have simply stuck with self-publishing, but I felt one of my books might be better off in a different setting. So I accepted an offer. However, I didn't sign without reading. I particularly insisted on a clause whereby I could regain my rights to the book. It was performance based. If the publisher had not delivered a certain number of sales in a specified time frame, the rights would revert back to me
They didn't reach the target, and I asked for my rights back. I'm not a lawyer, but I want to make the point that if a publisher wants your book, they should be prepared to negotiate the terms of the contract.
Personally, I'll just self-publish. It suits me.