Re: The Picture in the House
The factual error in this story would probably not even be worth remarking on if it weren't that Lovecraft himself would probably have been appalled had he realised his mistake. I agree that this story stands apart from the more cosmic, weird horror Lovecraft specialised in - but it is a notable tale in his development as a writer, I think.
Lovecraft's evocation of the horrific possibilities of New England hinterlands with their legacy of fanaticism and isolation is an early example of his usage of regional atmosphere as a backdrop for his tales. He may have taken a cue here from Hawthorne and Gorman, but it was an approach that he would make very much his own. As J.D. notes, The opening passages are notably strong and the whole sequence re: 'searchers after horror' can serve as a cornerstone for the whole move from mystical, Gothic settings to horror that is grounded in places the writer personally knows and can depict in that much more vivid detail.
The picture of the old man, a man who might even have been impressive and worthy of respect if not for his squalid, slovenly condition is very vivid and resonated with another thread that runs through many of Lovecraft's works.
While the actual horror here is more the sort of thing that would later be milked by Tobe Hooper, it's worth noting that Lovecraft may have been there first. Definitely a creepy tale with a great slow-dawning of horror, although the over-fortuitous ending is a serious weakness, in my opinion.