Coming up with titles is so difficult. Adultery for Beginners is the only book that picked up its final title early on in the writing process. Since then it's usually the final stage in the process of writing and involves me suggesting long lists of titles to my editor, and her sweetly commenting that she thinks I'm not quite there yet.
So the books are actually written using a working title. It's ended up that I use something that makes me laugh and feel positive about the book whenever I see the title:
Nice Girls Do was written as A Single Girl's Guide to Hedging and Ditching.
Another Woman's Husband was The Sex Life of Hamsters
A Single to Rome was Thirty Eight Bonks
Kissing Mr Wrong was Sexgod and Love Bunny
At the moment the new book is under a file marked Questbook, but I really think that's going to have to change.