Huh? Newt created a book consisting of a compilation of his old speeches, published it himself, and sold it by the case to his contributors? I don't think so. Gingrich made a book deal from HarperCollins that included an advance, not unlike both Bill and Hillary's book deals.
What ultimately brought down Gingrich was all of the ethics charges made by DemocRATs, all of which were ultimately dismissed.
Ultimately what caused Newt to resign was his extramarital affair.