More inadequate than ""informal,"" this sketchy, poorly organized chronicle of mystery fiction--often little more than an annotated listing of authors--is by two Italian writers identified only as ""students of detective fiction."" With virtually no critical remarks or real tracing of developments, Benvenuti and Rizzoni ramble from Poe to Conan Doyle to Nick Carter to Chesterton--summarizing plots, recycling the usual sub-genre labels, tossing in chatty bits of trivia. And, as the number of writers escalates in the Thirties and Forties, the book becomes chaotic, while the authors apportion their space in an often-bizarre fashion--which may or may not be indicative of Continental attitudes toward English/American mystery fiction. Earl Derr Biggers (Charlie Chan) is chosen as one of the five major figures of ""The Golden Age."" You'll find Margery Allingham at the end of a chapter called ""American Detective Fiction Comes of Age."" Stuart Palmer and Mignon G. Eberhart each get about four or five times as much space as Ngaio Marsh; Michael Innes appears only as one name in a list of near-forgotten 1930s Britishers. Dubious sweeping statements abound: ""Cornell Woolrich was not only the creator and the greatest exponent of the suspense story, he was also a novelist whom many consider the equal of Edgar Allan Poe."" And the mystery since 1945 is covered in a skimpy guest chapter by Edward D. Hoch--who, hard as it may be to believe in 1981, relegates the likes of P. D. James and Ruth Rendell to a category called ""Women Mystery Writers."" (Equally dunderheaded: Tony Hillerman's fine books are pigeonholed under ""Ethnic Detectives""; and dozens of US hacks are mentioned, while such major non-American figures as James McClure are entirely left out.) The only asset here, in fact, is the relatively extensive material on French mystery fiction. Otherwise: a shoddy assemblage, without any of the style, class, or humorous intent of Murder Ink--and inferior in every respect to Julian Symons' Mortal Consequences.