My first was Rats in the Walls. Somehow, it felt overrated to me. All the same I read other Lovecraft stuff over the years. Those involving alien intelligences and the like, they didn't suit me. But there was one which bothered me and I can't remember the title anymore.
Anyone remember the one where you have an old man who never dies, and who has lived for all those years in New England plotting and planning something? I think he had a house with weird things underneath.
Not quite an accurate synopsis, but recognizable, I think.
The Case of Charles Dexter Ward, I believe, is the one you're talking about. Ward was a Salem merchant who left there at the outbreak of the witchcraft scandal and came to Providence; he didn't age noticeably, and his peculiar actions eventually called down the notice of the more prominent men of the time. So he was killed -- by them, or by ignoring the injunction of his colleague to "doe not calle up any that you cannot putte downe"... but he had made plans, and left clues, and his descendant Charles Dexter Ward, unfortunately, is the sacrificial lamb to bring Curwen back nearly 150 years later....
Does that sound familiar? There is a section in the novel where Dr. Willett is underneath Curwen's house, in the ancient vaults, and discovers what is at the bottom of some of those wells.....
As for "The Rats in the Walls", I notice that a lot of more recent readers (say, over the last 20 years or so) have had that response; yet I think it's a more subtle tale than is often realized. The rats aren't real, of course, but we're left uncertain whether they are actual spiritual phenomena, or a manifestation (in his own mind) of De la Poer's tainted ancestry calling him as the past reaches out to engulf him... and it has tremendous implications throughout the tale that are often missed, such as the fact that his is not only not an isolated case, but a synecdochical one, as he stands in for all humankind. There's also a lot of genuine folklore and history woven into that one (as with so much of HPL's work), including some very interesting aspects from S. Baring-Gould's
Curious Myths of the Middle Ages -- especially the chapter on Bishop Hatto and the legend of the rats and the tower.... Lots of subtleties to that piece, I find, so that it continues to grow with me over the years....