From the publisher's website:
UnSpeakable: An InSpectres micro-supplement of Lovecraftian horror, madness and mystery.
From the introduction to the product:
The basic play structure is that of InSpectres, except flavored with a 1920’s setting. Rather than agents working out of a company, the characters are people who have been called together to investigate the Unknown.
Naturally, there are changes to the basic rules of InSpectres.