There are 11 books in the Duke De Richleau series. The newest book is Dangerous Inheritance which came out in 2013.

3
The Second Seal

Book cover of The Second Seal
Spring 1914. At a masked ball, the Duke de Richleau has an intriguing meeting with a beautiful woman - an incident that was to lead to a series of desperate adventures with a Serbian; a secret; a terrorist society; then as a British secret agent at the Austrian Supreme Headquarters.…

5
The Forbidden Territory

Book cover of The Forbidden Territory
Dennis Wheatley's first published novel, introducing his modern trinity of musketeers in the epicurean Duke de Richleau, financier Simon Aron, and the wealthy young American, Rex Van Ryn.

The Duke receives a coded message from his missing friend, Van Ryn who, while hunting for treasure lost during the Soviet takeover…

6
The Devil Rides Out

Book cover of The Devil Rides Out
The aristocratic Duke de Richleau faces new, sinister challenges in this macabre tale of the dark arts. When his good friend Simon Aron's naive curiosity is tested, the Duke, along with his ever-patient friends Rex Van Ryn, and Richard Eaton, must intricately plot a means of both physical and spiritual…

8
Codeword Golden Fleece

Book cover of Codeword Golden Fleece
28 Jul 1939 - Oct 1939When the Second World War opened, the Duke de Richleau and his friends Simon Aron, Rex van Ryn and Richard Eaton–the indomitable four–were in Poland. Here is the story of how they came to be there and found themselves even before the outbreak of hostilities…

9
Strange Conflict

Strange Conflict
When the bombs fall on London, the elderly Duke de Richleau is forced to consider a problem of the utmost urgency. What methods are the Germans using to discover – with sinister effect – the secret routes of the Atlantic convoys? His answer is bizarre and fantastic. Could it really…

10
Gateway To Hell

By Dennis Wheatley , Dennis Wheatley ,

Book cover of Gateway To Hell
Why would a man rob his family bank to make off with more than a million dollars? Yet that is what Rex van Ryn seems to have done before vanishing without trace in Buenos Aires. The Duke de Richleau and his friends have their suspicions about the ex-SS Gruppenfuhrer with…

11
Dangerous Inheritance

Book cover of Dangerous Inheritance
First published in 1965, this is the final installment of the Duke De Richleau series...

The years have moved on, and De Richleau has relocated from his London pad to an apartment in the Mediterranean. His great friends visit on occasion, and on this one both Rex's son and Richard…