Lovecraft was an author born in 1890, died in 1937. He was inspired by the macabre tales of Edgar Allen Poe and his area of expertise was writing Weird Fiction, that is, pulp horror fiction. The only real outlet for this kind of writing was in pulp magazines, and as such he had one helluva time trying to scrape out a living. When the depression happened in 1929, it basically didn't affect him that much because he was so poor anyway.
His stories deal with the basic idea that the universe is indescribably immense, and we are but a small, insignificant part of it. This is essentially nihilism. In his stories, he embellishes this by inventing horrifying creatures from unknown dimensions or from untravelled voids that humanity knows absolutely nothing about. The main horror of his stories is in not knowing exactly what these things are, or how to keep them at bay, and also that you know that, in a way, they are more powerful, possibly more intelligent and quite probably more deserving than the human race: that we are, essentially, worthless and ignorant. The actual monsters themselves veer away from the typical blood/bones/ghosts/gore themes of Poe's fiction, and veer toward tentacles/fish/inbreeding/tainted blood/gelatinous entities.
Oh, and unfortunately, Lovecraft was a flaming racist. I like to think that he disliked almost ALL people and just saw his fears in the people of other races. Of course, this may very well be wrong, but I tend to read his stories and try to ignore any unfair, prejudiced slants to his writings. It's never Birth of a Nation racist, but I think pretty much all minority groups are only portrayed as members of evil cults. (With the exception of the Native Americans in the Curse of Yig, which he ghost-wrote for someone.)
I'm not actually a Kiwi, I just randomly thought it up one day.