Some hallmarks of the horror genre.

There are some clear signals in Lovecraft of stylistic elements that would later become commonplace in the horror genre. It's a pity, to some extent, that we got so used to these that by now they've become cliches. Even kids would use them when telling horror stories at night. Both the beginning and the end of Dagon, the first story in this book, are clear examples of this:

I am writing this under an appreciable mental strain, since by tonight I shall be no more. Penniless, and at the end of my supply of the drug which alone makes my life endurable, I can bear the torture no longer; and shall cast myself from this garret window into the squalid street below. Do not think from my slavery to morphine that I am a weakling or a degenerate. When you have read these hastily scrawled pages you may guess, though never fully realise, why it is that I must have forgetfulness or death.

(Lovecraft: p. 1)

Here is the end:

The end is near. I hear a noise at the door, as of some immense slippery body lumbering against it. It shall not find me. God, that hand! The window! The window!

(Lovecraft: p. 6)

They may sound tired to our ears, but one should remember that Lovecraft pretty much invented these and many other stylistic tricks.