Double or Quits by Erle Stanley Gardner (Corgi, 1964)

Another book from the Lifeline Bookfair.  This one is a bit battered, but it's still readable:

 

QUIETLY

 it began : with a hunt for a missing secretary and some stolen jewels.

COMPLICATING

the issue : blackmail and murder

FASCINATING
it became : with a rich divorcee and a lonely widow

CLIMAX

was when Donald Lam took a long drink from a bottle of poisoned Scotch.

There's something wrong with the the corpse depicted on the cover.  Oh, he's ghastly enough (who expects a dead body to be decorative?) but his head looks flattened out and distorted somehow, as if it had been run over by the car whose wheel we see in the top of the illustration.  He wasn't, by the way.  The victim in this murder mystery died of carbon monoxide poisoning.

Dud cover illustrations aside, there's a little bonus in the back of the book--Corgi was running a crossword competition and offering cash prizes to the winners:

£5--that was quite a lot of money in 1964!