I read his first novel, Deadline for a Dream, that was published in 1957 and translated in Finnish five years later as Ei armoa unille (which is a misleading title). In the book Knox uses his knowledge about working as a journalist as the main character in the novel - beside the leading cops, of course - is a young journalist who's fallen in love with a good-looking woman who wants nothing but the best. The young writer decides he'll rob the money car. There's something in the set-up that doesn't ring true to me, though Knox uses it to a good effect in the scenes in which the journalist guy does the story on the robbery and interviews the cops. The climax in the end is exciting, but leaves a bitter aftertaste when Knox's police heroes say that the guy was really a victim, the actual criminal was the babe who just wanted more money and furs and fancy restaurants.
Knox seems a reliable police procedural writer and I'll be reading more of him with some interest. I'm in the middle of John Creasey's Gideon's Risk (surprisingly the only Creasey novel translated in Finnish!) and see the tradition of the police procedural genre in England. There's also Leonard Gribble. (He and Creasey also dabbled in westerns, by the way, Creasey wrote as William K. Reilly and Gribble as Stetson Cody. Anyone read those?) Any other names you care to mention?
Oh, here's someone writing about the five translated Knoxes in Finnish. I don't know the illustrator of the Finnish paperback edition, but it's a scene right in the beginning of the book.