I have been reading/listening to a lot of Lovecraft lately and will be doing a review in the next few days on the stories I have gone through. While there is no doubt that he had an awesome inspirational effect on horror/weird writers to come and he was very clever in his invention of an entire area of New England in which to base his stories, overall, his writing isn't really that good.
The stories are often repetitive, utilizing the same principles as a basis for each story and he often even repeats the same facts presented in a given story multiple times almost word for word within that story. Many of the stories go on too long and, in my estimate, he blows opportunity after opportunity to end the story in the right place and at the right time.
In essence, he's a one-trick pony and wears thin very quickly.