If I am being written about in a memoir without my consent and not in the most favorable light, what legal recourse do I have?

None, unless they are including lies or protected private information that may cause injury or incur damages.

If the memoir is based on true, verifiable public events or events that many people know about, you probably don't have much recourse. However, if the statements are false or exagerated or deal with very private matters, you may have a claim for defamation.