I travel a lot and I buy a lot of guidebooks that contain suggested walking tours, pointing out sites along the walker's path and this looks very much like a real guidebook. It even has the number "16" in the corner, suggesting that there are others in this same series.
But there are no other guidebooks in this series. It is false. Nearly everything in this book is false. The Shambles is purported to be a neighborhood in Chicago, but no such neighborhood exists. And if it did, it would probably not contain a house full of murderous grandfather clocks; or man-eating crocodiles; or Cereal House, where you must provide the name of your next of kin before daring to spend the night.
Still, Gaiman and Wolfe did their homework. They recommend that tourists visit the home of H.H. Holmes; Holmes was a real person. He was a notorious serial killer who murdered dozens of Chicagoans in the late nineteenth century. But his house of horrors was in Chicago's Englewood neighborhood and has long since been demolished. Chicago does have a Canal Street, but it is clearly not the dangerous Canal Street described in this book.
The House of Clocks does not exist, but it does have its own website.
http://www.preserveusfromthehouseofclocks.com/
While not among their best works, this slim volume is fun and funny, and scary, and it made me smile. Those of us who are fans of Gaiman and Wolfe will enjoy it.