SERVANTS OF THE WANKH

Ace paperback, 1969. Cover art: Jeff Jones.

"Marooned on the strange planet Tschai, Adam Reith agreed to lead an expedition to return the princess Ylin Ylan, the flower of Cath, to her homeland halfway around the globe. 

Monsters of land and sea lay before them, and beings both human and alien who might rob, kill or enslave them. Tschai was a large planet, an ancient planet, where four powerful alien races struggled for mastery while humans were treated as pawns; nothing would be easy for Reith on this journey. 

But the girl's father was enormously wealthy, her homeland technologically sophisticated. If reith was ever to obtain human aid in returning to Earth, where better than Cath? If he could get there..."

This is quite an infamous paperback; Wankh sounds like a particular example of Commonwealth slang that Jack Vance was unaware of at the time. He was convinced to change the offending word for Wannek in later editions.