From the back of the 128-page sourcebook/update:
"Happy New Year!
It's been one heck of a year out here in the Weird West. Before you knew it, Father Time was on his way out, and Baby New Year was sauntering into the saloon, loaded for bear. Deadlands: The Weird West started out set in 1876, but a lot of water (and a heap o' blood) has gone under the bridge since then. Now it's 1877 already.
If you've been watching closely, you know a lot of things have been going on in the Weird West. Well, that sure hasn't changed. Tales o' Terror: 1877 is packed with all sorts of details about the current state of affairs in War Between the States, the Great Rail Wars, and the rest of the West.
Not only that, there's a passel of new rules for heroes and Marshals alike, including new ways to make large fights run quicker than ever. With these, you can fine-tune your game until it purrs like a well-oiled steamwagon.
This book picks up where the ever-essential The Quick & The Dead left off, and it hits the ground running. If you want the real scoop on what's been happening in Deadlands: The Weird West over the course of the past year, you've come to the right place, partner!"