This book is connected to (and a sequel of) Ides of April which is part of why I enjoyed it, though I still prefer Ides.
Because the Goodreads synopsis sucks, I rewrote it:
Book follows a family, the father is a merchant and is gone at the beginning. The youngest is in school, and the older ones are all interested in various other things (animals, merchandise, teaching, etc.). The father and oldest travel together early on in the book, so the son can learn about the art of merchants. When they come home, they bring an unconscious man with them. He was found in the desert - he'd been tied to a galloping horse and dragged through the desert as punishment for something, and then left there to die in the sun. The youngest takes charge of him and tries to restore him back to health.
Things happen, the family falls upon hard times and has to cope with that, the youngest has to quit school and stay home to help. When the man can finally talk (his throat has been damaged due to dehydration after days in the desert), he can't remember who he is, what he did to receive such treatment, where he came from, or where he was going. As he tries to regain his memory, he helps the family in their struggle with poverty. They eventually rent their house out to the despised Romans who have taken control of the land and it is while the Romans are living there that the man starts unraveling the mystery of his past.