This story is great for grades 3-4, but I thought the pacing suffered mainly in the beginning. I am not a fan of flashbacks and I thought they slowed the action too much. Jackson's interest in science gives him a different voice and his friendship with Marisol adds to the story, but both characters' voices sounded old at times. It felt like the narrator, as an adult, was speaking to me the reader. This doesn't happen all the time but it did enough to jar me out of the narrative text.
Crenshaw is Jackson's imaginary friend who appeared in his life when he was seven but then disappeared after the situation was resolved. Jackson doesn't want to have anything to do with Crenshaw because an imaginary friend is far from science and facts. But as his situation gets worse, he turns to Crenshaw for advice and sympathy.
Jackson's dad has multiple sclerosis and it has sent their family in a downward spiral with medical bills and job loss. His parents always try to look at the bright side and hide their problems from their two children, but Jackson knows the signs when they sell everything and start to talk about wanting a "money tree". Homelessness is presented in a way that won't frighten the young reader but as an adult it seemed glossed over to me. You'll have to decide for yourself. A quick read.