I, Libertine, By Frederick R. Ewing. 151 pp. New York Ballantine Books. Cloth $2.75, Paper 35 cents In one of the few completely honest blurbs ever to appear on a book jacket, the publishers describe this novel as "turgid." My copy of Webster's World Dictionary defines the adjective as "swollen; bloated; congested; distended beyond its natural state by some internal agent or expansive force," a pretty fair description of eighteenth century England and certainly not inappropriate to much of Frederick R. Ewing's style. Nevertheless, readers who enjoy their geneology served up with sex, and unraveled at a twentieth century tempo, will find much to their taste in this be=bop minuet base on the life of Elizabeth Chudleigh, Duchess of and her unacknowledged heir, Lance Courtenay. Bawd (Lilith Axelroad) meets Libertine (Courtenay), who ison the make - not ofr a loveaffair but a title. Bawd loses Libertine when she discovers that they are both offspring of Lady Chudleigh. Libertine loses title when he unwittingly helps Miss Chudleigh void the marriage that made him an Earl. Throughout, the characters are depicted in a manner that suggests, at times, that they might have descended not from English nobility but contemporary spacemen. Mr. Ewing views his people like a discriminating headhunter. Of Courtenay - "His teeth were excellent, especially the upper right incisor." Of Miss Axelrood - "She had unusual ears." "Mr Ewing" (the pen name of Theodore Sturgeon) is himself afflicted, to a degree, with tongue-in-cheek. "I, Libertine" has been termed by Publisher's Weekly "The hoax that became a book." Originally, the hoax was launched by Jean Shepherd, an all night disk jockey who sent his listeners (the Night People) into bookstores in quest of a "classic" that did not exist. Mr. Ewing came to the rescue - i.e. the book was co-authored by the team of Shepherd and Sturgeon. "I, Libertine" is history once over slightly.