The weird life of Vincent Techler

I say this with all seriousness.
I normally do not reveal much about my sources.
But this source is placed within the Peoria Public Library.
The source has access to the list of books being rented out by card holders.
He/she recalls witnessing Vincent Techler -- the missing husband of murder victim Melissa McMahon Techler -- buying some books during a recent book sale. One book was a handmade copy of something called the "Necronomicon." It looked fake, and it's didn't have a price tag on it. So it was sold to Techler for one dollar.
A week later, Techler's wife was dead.
And one day after this wife was murdered, but before her body was discovered, he showed up to research two books. They were called "The Whitby Murders: A Case Study" and "The Van Helsing Family Journals." I do not have the books in front of me, but I am told they constitute some sort of vampiric horror story, and purport to tell the "real" story of a vampire's attack.
The Necronomicon is a fictional work by several authors. I am told that several people who love this sort of stuff imagine it to be real. There is no accounting for taste.
This source talked to police. They never asked about that books in which he had an interest.