Be Frank with Me by Julia Claiborne Johnson

One of the most memorable characters I've come across in a book lately has to be young Frank Banning of Be Frank with Me. Frank is the son of reclusive writer MM Banning, who had one huge hit then vanished from sight. But after losing her fortune in a Ponzi scheme she needs money so has agreed to write another book. Her editor sends out Alice Whitley to move the process along and help MM (Mimi) with whatever she needs--which mostly ends up being taking care of 10-year-old, high-maintenance, brilliant, probably Asperger's Frank--who loves to dress up like characters from old movies and spout facts about anything and everything.

Alice is the voice of reason in this crazy household--which also sometimes includes a chiseled handyman called Xander. She tries to keep the prickly Mimi on track with the book, tries to keep the household running, and tries to be there for Frank--over whom she becomes very protective.

It is a sweet and crazy story with a lot of unexpected turns.