QUESTION: My ebook contract is coming to an end soon, and I want to pull my book rather than let it remain. How should I go about this?
The standard method in publishing is to send a signed, registered letter stating that you want the return of your rights. (The process is a bit more complicated when it involves a large publisher.)
If this is a case where the publisher seems to be stonewalling you or is ignoring you or the business itself, you should quote a deadline like "If I do not hear from you about this within three months of your receiving this letter, I will assume your agreement in this matter." (Be sure to keep the return receipt from the letter so you'll have legal proof!)
Be business-like and to the point. State what you want, the legal reason why you can get what you want (the reversion of rights clause in the contract), and the particulars of the reversion like "this contract was for two years and was signed by you on this date."
You shouldn't state your unhappiness with the publisher or anything like that.
Nor should you feel bad about doing this. Publishing is first of all a business, and you are in business for yourself, not for anyone else.
If the publisher tries to bully you, and you know you are within your rights according to the language of the contract, stand up for yourself.
Some author organizations offer help in these matters, and some experienced professional writers are also helpful in clearing up contract confusion. Ask around if you are confused about contract language, etc.
Of course, the best thing to do is to understand the contract in the first place before you sign the dang thing.