SOLVED. Author's last publication, a mystery book that takes place over 31 days in 31 chapters with a prologue. [s]

[Wei]

EDIT: Book's found! Roger Zelazny's A Night in the Lonesome October.

I recently (within the last week) saw a post on tumblr or Twitter about a book with a bunch of characters that plot against each other. They fight over either an inheritance or the fate of the world, and murder is involved.

The book contains thirty one chapters, one for each night, as well as a prologue.

This was the author’s last book published before they died.

The cover art has a cozy fireplace-lit living room full of characters, about twenty of them including a dog in the lower right corner.

George RR Martin has a quote on the cover page about it being great.

[Ayshe]

A Night in the Lonesome October? This edition's cover: has George RR Martin quote.

[Wei]

That's the one! I spent way to much time today trying to Google variations of "night" and "October".

Thanks!