But does Vance actually have "two sets of books?" I think what he's got are documents where Weisselberg stated under oath some property was worth X and then in another said it was worth Y. THAT'S NOT WHAT WEISSELBERG'S being prosecuted for now, btw.
There are indeed two sets of books. Weisselberg makes $970,000 a year. One set of books says he makes much less, but that decrease is offset by company expenses for tuition, company car, company apartment etc. whose total exactly matches the decrease in Weisselbergs W-2 salary.
It appears to be true that Weisselberg treated things like cars and tuition as "non income," while the Trump company expensed them as income, and Don personally signed the checks. Apparantly Trump inc didn't withhold tax or pay payroll taxes on the "perks." But so what? Weisselberg gets convicted, and he and Trump pay some money/fines
To get the Don, Vance has to get Weisselberg to say "Trump told me to put different values on property so he could get loans and avoid taxes."