Condition Continued: There are no markings in the book. No attachments of any kind. And no one has written their name or anything else anywhere.
You can see the dust jacket in the first few photos. I have always had it in a fitted protective cover. It's an oxymoron: the jacket, front and spine, is white and clean. It doesn't have any tears. The white flaps are perfectly clean. There aren't any tears on the flaps. There is one thin crease just below the front flap's top corner. The jacket is NOT price-clipped, not clipped at all. 

The MacMillan Company, New York, 1967. Hardcover in Dust Jacket. This is the Danube Edition. On the copyright page is stated 'First Printing 1967 '. I'm assuming that it is the first printing of the Danube Edition of this novel. The Gladiators was first published in 1939. 
  The Gladiators was Arthur Koestler's first novel and the 'first of his trilogy of political novels that probe the great dilemma: does the end justify the means?'. It is a 'historical novel of Spartacus and the Slave War against Rome. The other two in the trilogy are  Darkness at Noon and Arrival and Departure.' Of The Gladiators the New York Times Book Review stated 'An Olympian book. It looks down on humanity with age-old eyes and discovers with a kind of cynical joyousness that the man-eating pattern of history is a timeless design.' A blurb from The New Statesman: 'One reads The Gladiators for its political implications and questions, above all the question of doing evil that good may come. It is a book which anyone who was wondering what will happen to us will do well to read.'