This article is called H.P. Lovecraft's Commonplace Book, and is described as:
"This book consists of ideas, images, & quotations hastily jotted down for possible future use in weird fiction. Very few are actually developed plots—for the most part they are merely suggestions or random impressions designed to set the memory or imagination working. Their sources are various—dreams, things read, casual incidents, idle conceptions, & so on."It's a transcription of his notebook. I haven't actually finished going through it all yet, but what I saw looked really interesting. I think it would be great info for anyone interested in old "weird fantasy" pulp stories, or of course if you're playing in or running a Call of Cthulhu campaign.
I also just did some Googling around, and if you want to spend $300 for a new copy, you can order the entire transcribed book which includes:
"...his theoretical ideas about writing weird fiction and the commonplace book which spans the years 1919 to circa 1935. Part One includes "Suggestions for Writing Story", "Elements & Types of the Weird Story", "A List of Basic Underlying Horrors". Part Two includes many references to his weird creatures and even weirder ideas, many he never got a chance to use. Cover art by Steven Mendelson."