The Shadow Over Innsmouth

The Shadow over Innsmouth is great a horror novella by H. P. Lovecraft, written in 1931, which forms part of the Cthulhu Mythos, using its motif of a malign undersea civilization. It also makes references to several shared elements of the Mythos, including place names, mythical creatures and invocations.
The narrator, who is a student on an antiquarian tour of New England, sees a piece of exotic jewelry in a museum, and learns that its source is the nearby decrepit seaport of Innsmouth. Then he travels to Innsmouth and observes disturbing events and people.
This is the only Lovecraft story which was published in book form during his lifetime.

Howard Phillips Lovecraft (1890 - 1937) was an American author who achieved posthumous fame through his influential works of horror fiction. He was virtually unknown and published only in pulp magazines before he died in poverty, but he is now regarded as one of the most significant 20th-century authors in his genre. Lovecraft was born in Providence, Rhode Island, where he spent most of his life. Among his most celebrated tales are "The Call of Cthulhu" and "The Shadow over Innsmouth", both canonical to the Cthulhu Mythos. Lovecraft was never able to support himself from earnings as author and editor. He saw commercial success increasingly elude him in this latter period, partly because he lacked the confidence and drive to promote himself. He subsisted in progressively straitened circumstances in his last years; an inheritance was completely spent by the time that he died at age 46.