I found this book in a trash bin and decided I should at least salvage its illustrated cover.
The book, originally Assignment - Treason is the second one to come out in Edward S. Aarons' Assignment series that took its protagonist, Sam Durell all over the world. The books are at least serviceable, if nothing great to my mind. The Swedish edition came out in 1959 from Wennerbergs Förlag, translated into Swedish by Margareta Sahlström. The illustration is by Mitchell Hooks. It wasn't originally meant for this book. "Förräderi" means "treason" in English.