The Dain Curse, by Dashiell Hammett, originally published in 1929.
It was a simple case of missing diamonds. The diamonds were not worth enough to attract the number of murders that followed. Of course there was something else going on, with someone else involved.
Hammett is brilliant with his writing. It doesn't take too many of his books to know we've met the perpetrator fairly early on. It is the "why" that is always worth the read.