The kiss quotient / Helen Hoang.

Enhanced descriptions from Syndetics:

Stella Lane thinks math is the only thing that unites the universe. She comes up with algorithms to predict customer purchases--a job that has given her more money than she knows what to do with as well as way less experience in the dating department than the average thirty-year-old. It doesn't help that she has Asperger's and that French kissing reminds her of a shark getting its teeth cleaned by pilot fish. She decides that she needs lots of practice--with a professional--which is why she hires escort Michael Phan. The Vietnamese-Swedish stunner can't afford to turn down Stella's offer, and he agrees to help her check off all the boxes on her lesson plan--from foreplay to more-than-missionary position... Before long, Stella not only learns to appreciate his kisses but also to crave all of the other things he's making her feel. Their no-nonsense partnership starts making a strange kind of sense. And the pattern that emerges convinces Stella that love is the best kind of logic.