Lorenzo lives on a peach farm with his mom and grandpa (Double). His dad was killed in the military. The family is struggling and mom is always stressed about money. When the pig has a litter they are all sold off. Then the dog Bella also has a litter of puppies and it is discovered that the runt pig was missed. Bella raises Marty as her own and he grows up thinking he is a dog instead of a pig. He is Lorenzo's constant companion but his growing size means he gets into trouble quite a bit. 

Lorenzo's best friend is Paloma who has aspirations of being a singer. She is quite good and accepted into an elite school and camp. While she is gone Lorenzo learns a disturbing truth about his father. He also has to figure out a way to save Marty when mom threatens to sell him off. 

I enjoyed this book way more than I thought I would. Animal stories are usually not my favorite, but I enjoyed Marty. I felt sorry for Lorenzo and their financial situation, but I thought the mom was occasionally just mean. I did love the relationship between Lorenzo and Paloma. It is always nice to see best friends from the opposite sex who have to romantic interest in each other. I was glad Marty didn't die in the end and I think his ending was probably the best possible outcome. It still made me really sad.