"A White Merc With Fins," by James Hawes. Pantheon. 289 pages. $22 Accountant or bank-robber? Accountant - thief? What's it gonna be? Bank-robber - thief - terrorist - accountant, NO. OK. Settle on robbing a bank. It's a career decision. This funny, irreverent, fictional account of a 28-year-old's moving-into-adulthood anxiety is - yes - refreshing. Its modern-day, stream-of-conscious-prone criminal-protagonist explains the life he leads and what drives it. At the same time, he leaks only the details needed as he activates "The Plan," to heist a fast million. That holds the suspense. This book will make you snort out loud, at what seem like the most inopportune moments. It's written for anybody who's ever, but never seriously, been torn between the straight and the crooked life.