I used to read it to my kids, maybe 10 years ago. It’s a story of a boy who shrinks himself down to go into his own ear and see how memories work. He meets lots of different characters as if he is in a factory. Ultimately after all the process, all his thoughts and memories are dumped in a giant pile in his head. Finally he finds (remembers) what his mom told him when he finds a red letter in the pile. It was beautifully illustrated and really funny. I think the boys name was Max last name seemed to be Mc-something, McGinty? Please tell me someone can assist! Thank you in advance!!