The Bright Side of Disaster by Katherine Center
When very pregnant main character Jenny's fiance walks out on her , she finds herself on her own by giving birth that night. Turns out, being on your own is something that you are more capable of than you thought, as Jenny gets into a groove with her newborn. She learns who her friends are and finds that sometimes you come out better in the long run and disaster isn't as bad as it seemed.
If you are looking for a good/easy summer read, pick up anything Katherine Center. You won't be disappointed.