This is more a series of mini-adventures than one single novel, in which Hercule Poirot and his devoted friend Hastings try to thwart the plans of an international gang known as the Big Four in the quest for world domination. Despite the global influence of these criminal masterminds, Poirot engages them in a war of minds and strategy that has likely deadly consequences.
The Big Four is one of the most unashamedly entertaining Christie novels I've read, with a Shakespearean penchant for unfathomable disguises, plenty of melodramatic grandstanding, and a few satirical digs at the conventions of mystery-writing.
Seen from the sidekick Hastings' point of view, the reader is kept in the dark for much of the novel, while being given plenty of clues to make guesses at the resolution. A fun, light-hearted read of a detective novel.
Next up: The Secret Adversary by Agatha Christie (the last in this three-novel volume, and I'll move on to something different!)