This is an excellent one-shot adventure, and one certainly can't quibble with the price. Production values are pretty good, and the plot, though it tends to force the players into a specific path, has some variability in it allowing for certain side adventures. There is a brief sketch of Tombstone that provides enough information to play it to the extent necessary for this adventure. Eight pre-generated investigators are provided, including two women in case your group has any ladies in it. The encounters aren't too pre-scripted which gives the players some opportunity to vary the outcome in each individual case. The various confrontations aren't particularly deadly, though the final scene can be very bloody indeed. The author has also provided some adventure seeds in case you want to use the scenario in an extended campaign. In fact, this could be a very good starting scenario for an old-west campaign setting, though it would require some significant work in order to ensure the players can develop a gradual understanding of the mythos despite being forced to confront the monsters at the end -- still, they aren't major monsters and they are different enough that they could lead to further complications later on. Finally, it would be an interesting change of pace for your group, even as a one-shot adventure (and would result in an interesting back-story to a new threat arising in the classic or modern era...).
All in all, its an excellent effort with general verisimilitude to the western culture, (barring one glaring mis-reference to the "Pony Express" which apparently used wagons to deliver the mail in the author's world, instead of riding ponies and carrying the mail in their saddle bags.)
Overall I gave it a four for being a one-shot adventure as well as being somewhat "rail-roady" in its nature. Anyway, as I noted earlier, the price is right, and I strongly urge you to acquire a copy while you can!