Actually, these are not the most egregious spoilers I could throw out there, but consider yourself warned.
Among the books I've read recently are two time-travel novels. I always enjoy seeing how an author deals with the inherent paradoxes that go along with time travel. Each of these books left me with an unanswered question that, while not the biggest deal in the world, nagged at me nonetheless. Why? Because I'm a nitpicker. It's what I do. Deal with it.
First book: Destroyermen - Into the Storm by Taylor Anderson.
This one starts with a cool premise. During WWII, a particular battle in the Pacific has not gone well for the Americans. Two ships are following orders and trying to flee instead of needlessly sacrificing themselves. The Japanese Navy is on their tails and is gaining on them through a day-long chase. An unusual storm appears and they use it to take temporary refuge. Sailing out of the other side of the storm, the crews of the Destroyers discover they're not in Kansas anymore. (Dude, it's metaphorical!)
Anyway, we discover that this one isn't actually time-travel per se. It's more of dimensional travel. As far as we can tell, they're still in 1942, just a different 1942. In this one, there are no humans (that they can find), but two other dominant species with varying technologies and language skills. And there's dinosaurs. This is what 1942 might look like if Evolution had gotten sidetracked somewhere along the way.
One story point is that they have to find oil so they can refine it and make fuel for the Destroyer. There's a scientist aboard who predicts that since the geography (and geology) seems to be almost identical to the world they came from, there should be oil in the same places as well. They drill where he says there's a large deposit and, Yay...OIL!
Here's my question. My simple science education told me that oil is dead dinosaurs...or more specifically, the result of a sudden catastrophic event that caused most, if not all life, on earth to have died off suddenly. The deposits of these rotting carcasses and vegetation is what eventually became oil. So if they're in a version of Earth where the dinosaurs didn't die, what made the oil?
Book Two: Time Spike by Eric Flint & Maralyn Kosmatka.
In this one, there's a phenomena that shows up and physically transports a small piece of geography millions of years into the past. In this case, the geography is a Maximum Security Prison with all of the prisoners and its short staff of guards. What's more, as things progress, they discover that this phenomenon hits the same piece of geography over and over again at random dates as it goes back in time. The denizens of the prison soon discover that they're not alone in their displacement. There is a prehistoric tribe there and also a group of bloodthirsty conquistadors with Hernando De Soto in charge.
My question for this one? If the phenomenon drops in on the same spot at multiple points in time, why don't the prison guards have to contend with folks from their future as well as from their past. I really expected them to encounter someone from their future as I read the book and when that didn't ever happen, it just seemed wrong.