You know what happens right after Casablanca's Rick Blaine (Humphrey Bogart) walks off with Capt. Louis Renault (Claude Rains) into the mist?This novel. Walsh, a former crime reporter and Time magazine music critic, can't equal the beautiful relationships in the classic film, but he does give us a clever takeoff on the tale, with less romance but much more action. As Time Goes By is both a prequel and a sequel, fleshing out Rick's mysterious life by flashing back to his 1930s New York gangland past and taking us with him, Ilsa, and Sam the piano man as they plot to kill Reinhard Heydrich, the Hangman of Prague. Rick Blaine started out as Yitzik Baline, who learned to shoot in the booze-fueled underworld of Tick-Tock Shapiro and Dion O'Hanlon. A fracas that made Walter Winchell's column explains why Rick wound up in the Casablanca gin joint. Ilsa undertakes to seduce Heydrich--chastely, if at all possible--and set him up for the kill. (He was the only top Nazi the Allies bumped off.) Filled with real history and deductions from the flick, Walsh's book is much smarter than Scarlett: The Sequel to Margaret Mitchell's Gone with the Wind, but purists will prefer to revisit the 50th-anniversary video edition of the film, or read the excellent making-of book Round Up the Usual Suspects. If you crave more heresy, check out As Time Goes By, a novel by Humphrey Bogart's son. --Tim Appelo