Abebooks by Between the Cover--Rare Books, Inc., all once stored in the carriage house of Stout's home.
Better yet, some of them were rated by him:
Christopher Hale, Rumor Hath It (1945) (B+)
Helen Reilly, Murder on Angler's Island (1945) (B2) (they don't know exactly what the 2 signified)
Christopher Hale, Hangman's Tie (1943) (S) (?)
Ethel Lina White, Her Heart in Her Throat (1942) ("surrender on p59") (Oh, Ethel! TPT)
George Harmon Coxe, Murder for Two (1943) (A-)
William L. Stuart, The Dead Lie Still (1945) (C+)
There are other books, but I didn't see others with ratings. I have to say Stout's Ethel Lina White comment is hilarious, even though I quite like this author. I don't believe her later books, from the 1940s, are that good, however. Have you read any of these books? Was Rex Stout right that George Harmon Coxe was the best bet? I'll be talking more about Mr. Coxe soon.