I have no idea what this is, I happened to chance across it while looking for info on another book at the ibooks Web site. Here's the description:
Eckels, a psychotic time traveler, has shot a dinosaur and meddled with history, destroying the future and trapping himself in the past. Transported to an alternate prehistoric period by a savage timestorm, Aaron Cofield manages to link up with a Travis, a lost Time Safari guide. Together, they must hunt down Eckels and restore the shape of history. Attacked by sentient dinosaurs, Aaron and Travis escape to an alternate medieval Japan. Caught between dinosaurs, ferocious samurai warriors, and the cold-blooded Eckels, the two must fight for their own survival—and to restore the timestream of our future!
So "Ray Bradbury Presents Dinosaur Samurai" is apparently something loosely based off of Bradbury's "Sound of Thunder" and just filled with as many crazy things as the authors (Stephen Leigh and John J. Miller) can throw at it.
It includes both dinosaurs and samurai and so seems built for me. I may have to pick it up.