Gary Gygax's The Samarkand Solution is the third book in a trio featuring Magister Setne Inhetep, a priest-wizard detective in a quasi-Egyptian fantasy world. Although Planet Stories published the three books out of order, each is a standalone novel and (as far as I can tell) no mention is made of the other stories in each book.
The mystery starts out quickly in The Samarkand Solution, as Inhetep spots a well-known assassin in a pub and trails him to the grounds of a Temple of Set. Inside, Inhetep discovers the Prince Governor in the midst of a mysterious gathering of foreign dignitaries. Seconds later, the Prince is murdered by presumably mystic means, but no trace of magic remains. Unlike previous books in the series, Inhetep investigates this mystery without the help of his loyal bodyguard Rachelle. Instead, he's joined by a local law enforcement official named Tuhorus (Inspector Lestrade to Inhetep's Sherlock Holmes, as it were). Along the way, they rescue a nubile slavegirl named Xonaapi, and some of the funniest passages in the book come from her attempts to seduce the quite proper Inhetep.
As before, Gygax has created an interesting fantasy world that is quite distinct from the generic medieval England fantasy worlds that serve as the background for so many novels. The characters and dialogue are good, and the combat scenes fairly interesting (though one can detect some D&D tropes in Gygax's penchant for secret doors and underground labyrinths). As a mystery novel, there are some flaws that could be frustrating to some readers: crucial clues necessary to the discovery of the murderer come from out of left field and are not known beforehand to the reader, so even a clever reader who carefully assembles the evidence, parses dialogue, and assembles a timeline would have no chance of solving the mystery before Inhetep announces the solution. As a fantasy novel this book is solid, as a mystery novel not so much.