From the author's website:
Ben Coffin knows from foster care that people can leave you without a good-bye. That’s why he prefers to hide out in the Coney Island library with his sci-fi novels, until he rescues an abandoned dog from the alley next door. Scruffy little Flip introduces Ben to fellow book lover Halley—yes, like the comet. Some call her Rainbow Girl for her crazy-colored clothes, but for Ben it’s her laugh, pure magic, the kind that makes you smile away the stormiest day. Rainbow Girl convinces “Sci-Fi Boy” to write a novel with her. What begins as a time-travel story ends up a mystery, one that has haunted Ben for as long as he can remember: If friendship is the greatest treasure of all, why can’t it last forever? Paul Griffin’s middle-grade debut will warm your heart as much as it breaks it with the story of two unforgettable kids at the crossroads of love and loss, helping each other find their way home.
He also repeatedly referred to women's and girls' bodies in sexual terms, saying that the female principal of the school has "a nice butt", and asking if the main female character has "a nice butt". Not only this, but one of the characters has a good time gazing at the "chestal area" of the same female character - so much that she notices him and calls him out on it (but not very strongly).
One might assume that the dog is a main character, but obviously this is one of those examples of not picking a book based on its cover. That said, there are blatant statements of a cat licking its "butth___" and then licking a character and of a dog that enjoys "h_mping" people's legs.
Finally, in perhaps the most offensive misuse of the English language, Mr. Griffin has a character exclaim the phrase, "Cheese Whiz Crust!" He tried as hard as he could to including a vain use of Jesus Christ, perhaps thinking that's how people (and kids in this instance) talk to one another. I am definitely more strict than most these days, but this is blatantly offensive even in its euphemistic form.
Besides this, repeated reference to the main boy's "Mom" and her deceased partner, Linda, was unnecessary to the story and seemed to be included simply for the purpose of giving a reader pause. Then there is the quick dismissal of an uncle who suddenly becomes a scapegoat for getting the main character out of a "home" situation that Griffin didn't want him to stay in. The whole situation with the uncle seemed forced just to have main boy Ben move in with his female friend's family.
Then the story switched to a story about the girl's cancer. Halley appeared to have her head on straight all along, and Ben appeared to work through some serious struggles (past and present), but Ben really doesn't react to the struggles of Halley's failing health and death like most of us would. Yes, that's a spoiler: too bad.
There is one redeeming aspect embedded in this story, and that is a mysterious box that the two kids create. Halley knows what's in the box, but Ben doesn't realize it until her passing and a note left in a secret location by his friend. There is a sweetness and a rich self-discover in that sharable moment at the very end, but it wasn't enough to make me want to keep this book on my shelf.