I don't like post-20th century paranormal books because they are such trite renditions on what could be a truly terrifying genre.
I am prejudiced against first-person stories that remind me of the rise of Mary Sue/self-inserts a la Fanfiction.net, circa 1998.
An immediate lustful encounter with a lifelong childhood friend? Really?! I thought the protagonists were trying to reenact parts of Twilight, unfairly hating the antagonists purely because they exhibited some era-appropriate common sense.
Points for portraying some period-relevant horrors: the influenza pandemic, WWI, racism against and subsequent hiding of German-Americans within society, the popularity of spiritual photographs.
But the main character had a lot going against her. She's named after Mary Shelley, yes, that one, and while I thought it was cute that she loves books (kudos for name dropping the great classics + some pop lit of the time) and she had a natural talent with mechanics, it drove me mad that she always had to have the last word in a conversation. It reeked of Mary Suisms whenever she actually conversed with another character or tried to push her holier-than-thou attitude on situations around her which showed the writer's contemporary values dissonance.
Ending was weak, I actually got it half wrong what happened because I was expecting something more sinister but... alas, opportunity wasted.