Like Dan Brown's "The Da Vinci Code," "Ghostwalk" has a background story that is factually/historically rooted - here it is Isaac Newton's alchemical research and its consequences - that is mixed in with a modern-day murder mystery.
The mystery has to do with animal testing in England and Europe and suggests that there is an animal-rights group that goes around killing humans to make its point that animals are sacred. After the original researcher mysteriously dies, a woman is hired to finish a book based on Newton's work.
She gets mixed up with the militant animal rights group and goes a bit bonkers when the 17th century surfaces in her current time/place. A contemporary of Newton's - a ghost, hence the name of the book - haunts her and her friends and tries to kill her! I just didn't buy it.
Overall, I thought it was preposterous, tedious, and icky. But if anyone wants to give it a go, I have a copy for you.