Charles Isherwood

'Mamma Mia!,' which weaves a few threads of romantic comedy around a bumper crop of old Abba tunes, is a thoroughly preposterous show, but it's also a giddy guilty pleasure, and its arrival on Broadway in a time of unforeseen anxiety has an aura of sweet inevitability. ('Spores, shmores! Let's boogie!') The show is already a certified hit, with an advance approaching $30 million, and that number will hang firm as word spreads -- in sheepish whispers, and from the unlikeliest of quarters -- about the genial good time it offers.