Ten novellas featuring circus-performer-turned-private-eye Mongo--"one of the greatest characters of recent mystery fiction" (Ellery Queen's Mystery Magazine).   With a genius IQ, a past career as a circus acrobat, and a black belt in karate, criminology professor Dr. Robert Frederickson--better known as "Mongo the Magnificent"--has a decidedly unusual background for a private investigator. He also just so happens to be a dwarf.   Originally published in leading mystery magazines in the 1970s, these ten novellas--each introduced with notes from the author--offer new readers and diehard fans alike a tantalizing taste of the unique blend of hardboiled mystery, science fiction, and explosive action of this acclaimed series.   In the House of Secret Enemies--which includes The Drop, High Wire, Rage, Country for Sale, Dark Hole on a Silent Planet, The Healer, Falling Star, Book of Shadows, Tiger in the Snow, and Candala--is the 9th book in the Mongo Mysteries, but you may enjoy reading the series in any order.