The 19th annual collection edited by the New York Times mystery/crime reviewer lives up to the title claim. Although it is a form of reviewer madness to try to note the best among the ""Best"" -- old pro Jack Ritchie's novelette The Operator is a cagily plotted story of an undercover policeman making good by doing bad better than his racketeer bosses. Fredric Brown is represented by a 38 word effort he calls on ""instant novella."" With forays into science fiction, adventure and the stalwart detective form, Mr. Boucher has made sure that there is something here for every . The book closes with the usual, handy lists -- awards, necrology for '63, the Honor Roll and an intriguing bibliography.