When someone goes book, or book mode, they have messed up. They were unintelligent , made a petty mistake, or were oblivious to something obvious. Being book is nothing to be proud of, so now it has been made into a meme
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".
I don't buy the schmegegge about Morty sleeping with Moira.
His version of the story was pure schmegegge.
The whole schmegegge was made up to get Liz a little bit of attention.