I had never read this book, but after seeing the movie and feeling like it could have been somehow more, I decided to check out the novel by Jean Hanff Korelitz.
I really enjoyed the movie, especially Tina Fey's performance, but I felt like where there could be depth, there was humor instead. The story is deep and touching on its own, but the writing and style of the movie lessened the depth for me.
The book, however, moved deeper in the areas I had felt were lacking. I really was interested in the effect that adoption can have 18 years later, when the son she gave up for adoption came back into her life as an admission officer, but the book really focused on her romantic relationship rather than on the issue of adoption. The book gave a lot of thought to the idea of adoption, especially when compared to the book.
The book commented on many aspects of adoption: there was international adoption, single motherhood, trying to cope with becoming part of an adopted family, and more. All of these storylines were present, some more developed than other, but it greatly expanded the depth of the overall plot.
The movie, though, is still great. More than anything, it is an adaptation that changes many things, while still remaining a great story involving some of the same characters. Where the book is dark and thoughtful, the movie is romantic and funny. I recommend seeing the movie and reading the book for the most complete experience with these characters!