This is a great question. Thanks for raising it! I just jotted down a bunch of titles and authors from the other moms' responses. I'm always looking for a good book.
I am currently reading one of the Shopaholic books by Kinsella, and I agree that it's a perfect read for a busy mom. I'm enjoying it. Another series with a little bit more depth is by Lorna Landavik. It's about a women's book club. I also really enjoyed reading Amy Tan's books. And I'm a huge Harry Potter fan. Ayn Rand is also great - Fountainhead and Atlas Shrugged are the best, but you definitely need your brain for those. I don't know about you, but my brain needs rest after my full day with the kids.
Personally, I cannot manage the extreme drama of some of the books I used to read before I had kids. I also don't have the emotional space for anything major happening to the characters. Divorce or anything really terrible happening to a child is just not something I want to read about right now! I also find that my mind doesn't have the capacity for serious literature right now. Maybe someday! We'll see!
I'm going to keep an eye on these responses, and if anyone can recommend any other books that are not too serious and don't have too much heavy drama, I'd love to hear about them.