All science fiction has some element of titillation — a strategy of taking known facts and stretching them to the limits of credulity, for the purposes of both entertaining and enlightening. But Crichton seems intent on confusing his readers, pummeling them with a barrage of truths, half-truths and untruths, until they have no choice but to surrender. As one of the author’s numerous stand-ins warns a naïve interlocutor, “Disinformation takes many forms.” Here, finally, Crichton has a point that should be heeded.

''Next'' would be a narrow, uninteresting book if its sole point were to condemn such tactics as transgressive. Instead Mr. Crichton moves far beyond questioning the morality of such experiments and acknowledges that they happen. His whole thriller-tutorial boils down to one troubling question, asked about each freakish breakthrough described here: Now what? Since ''Next'' is one of Mr. Crichton's more un-put-downable novels, the reader may experience some frustration. It's tempting to stop and look up each of the genetic, legal and ethical aberrations described here in order to see how wild a strain of science fiction is afoot. Save a step. Just believe this: Oddity after oddity in ''Next'' checks out, and many are replays of real events. ''This novel is fiction, except for the parts that aren't,'' Mr. Crichton writes, greatly understating the book's scary legitimacy.