And it's a heartbreaking tale. But the free verse didn't really work for me. I didn't see a compelling reason for it to be told in verse, besides that being what the author wanted to do (apparently it grew from a group of poems to a novel in verse). For instance, in the case of Inside Out and Back Again (a 2011 National Book Award winner), the use of verse complemented the story, which was being told by a younger child in a child's language. I felt like the use of verse also helped make the story more intense with that book. But in Under the Mesquite, I wanted more. I wanted more details; I wanted to get more inside Lupita's head and Lupita's world.
Maybe there's more to that than the use of verse. I suppose the author (Guadalupe Garcia McCall) could have gotten more in-depth while still using verse. And she did skim right through a lot of Lupita's life. It's a short book, only 144 pages (of verse, which has fewer words per page), considering the amount of time it covers and the potential depth of the story.
So while it's a good novel, I think there could have been more to it, free verse or not.