I recently finished these two books back-to-back and I must say, I haven't read books this entertaining in a long time. The protagonist is almost imperfectly yet charmingly adorable. It's a rare witty chick lit (a genre that is typically corny and plain to me nowadays) with a lot to relate to.
The first book (The Rosie Project) is about a genetics professor who is always struggling to maintain relationships with women (and also with people in general). So he devises a questionnaire to find the perfect partner. When he meets Rosie, a woman who doesn't fit his criteria (and failed his questionnaire), his world turns upside down in the most delightful way. The second book (The Rosie Effect) is about life with Rosie and more real-life struggles that he has to deal with beyond having a relationship with a woman.
If you're looking for the next book to read, try The Rosie Project first.