If you think the title's batty, try this for a chapter opener: ''The squad was somewhat perturbed. One might even say they were quite blaxitomed!'' Is the 77-year-old McBain losing his mind? As his wiseacre and battle-scarred omniscient narrator might say: Don't bet your fried corn husk on it, Gertie. The 53rd entry in the 87th Precinct series is top-dollar McBain, as funny and adroit as his last couple, but old-school edgier. What a joy to watch these same characters at work after 47 years, this time investigating the harbor-yacht kidnapping of a Beyonce-like pop star. Imagine your favorite Law & Order cast solving fresh mysteries into infinity, with no reruns, and you have some sense of McBain's grand, ongoing accomplishment.