''I'm Grace McGlone. This is Henry Dante. We're trying for heaven.'' So announces the heroine of Schickler's totally cracked, lushly written, but (as its title suggests) zanily uneven first novel. Grace is a small-town Wisconsin girl, Henry a reformed heavy carrying a suitcase full of stolen million-dollar diamonds. ''Trying for heaven'' means driving around the country after meeting at a car wash, giving the loot away as unforgiving gangsters give chase. Schickler ambitiously follows his fantastic 2001 story collection Kissing in Manhattan with a precious fairy-tale version of a bloody pulp novel. At times the book careers like a car without the brakes, but Schickler spins sentences in a way that keeps you in your seat.