Rain Reign - Ann M. Martin

Rose Howard has Asperger’s syndrome, and an obsession with homonyms (even her name is a homonym). She gave her dog Rain a name with two homonyms (Reign, Rein), which, according to Rose’s rules of homonyms, is very special. Rain was a lost dog Rose’s father brought home. Rose and Rain are practically inseparable. And they are often home alone, as Rose’s father spends most evenings at a bar, and doesn’t have much patience for his special-needs daughter.