I can't remember if this book was mentioned in Paperbacks from Hell, but I do know I discovered The Moonchild before knowing about that book. The cover, and the review I read (by Grady Hendrix, of course), was what sold me on it. I did go in to the book expecting it to be terrible, which might be the best approach for horror novels from this era.
To be fair, I didn't hate the book. I actually think McKenney's writing is decent. He manages to maintain a good tension through the book, which is pretty impressive because the basic premise of the book is stupid. The Moonchild (that's him on the cover) is a dead child who rises from the dead whenever he is struck by light and kills people by strangling them or tearing out their throats. Each kill makes him stronger, and the arm he uses to kill people gets larger, more demonic, and grows longer claws with each death. According to legend, the only way to stop a Moonchild is to bury him at the very spot where he was born, before his seventh birthday. Why? That's not clear, because no one in the story has any idea why this is the case (nor do they understand why the Moonchild curse even happens). I kinda wanted one of the characters to say, "Because the writer can't come up with a good reason."
I'll admit that Edmund Blackstone is the perfect name for a character in a horror novel, but I didn't understand why McKenney used his full name whenever he referred to him in the narrative. There weren't multiple Edmunds, and his wife wasn't consistently referred to as Anna Blackstone, so I can only guess that McKenney really liked the name, and wanted to get the most out of it. Either that, or he was paid by the word.
I actually considered giving this book three stars, but the end of the novel has a character appear out of nowhere to help make sure everything falls into place. There was something unnatural about him, based on how McKenney wrote him, but it was never explained, and didn't make a lot of sense. It was a little disappointing, because while I felt like the story was a bit dry and uneventful, by the time I hit the last fifty pages of the book, I didn't want to put it down.
I wouldn't recommend the book for anyone outside of horror, and even then, I would caution people to lower their expectations before reading it. I've certainly read worse novels, but there are a whole heaping lot of better ones I'd recommend before getting to this one.