This is Christie's first book featuring Superintendent Battle.
Adventurer Anthony Cade agrees to deliver a manuscript to an English publisher for an old friend. To Cade, this seemed like a simple favour, only no-one wants the manuscript to be published. The resulting capers have Cade crashing a house-party at Chimneys, embroiled in the politics of Herzoslovakia, searching for a Royal murderer and finding the infamous Koh-i-Noor diamond.
The book was FUN! The characters were interesting and enaging. As a murder-mystery it wasn't in the normal thrill-dash-ride for the killer. It was a bit of a mad romp through the idiosyncrasies of politicians, fanatics and aristocracy. None of whom seem even slightly versed in day-to-day realities.
So bring on the full English breakfast (minus the kidneys) and enjoy the farce as Scotland Yard and the Sûreté try to solve a crime with the bumbling help of a cast of characters who think it is all a bit of a lark - as long as the drinks are never delayed by a dashed inconvenient murder.