"Paradox" is a word that appears in just about every book about time travel that you've ever read. Our book this week, Kindred, is no exception to that rule. So what is a paradox? Why is it such a big deal?
Usually the best way to describe this is the "Grandfather Paradox". You travel back in time, and kill your Grandfather before he has offspring, but in turn, that means that you were never born. So you could never go back in time and kill him, which means that he would have kids and, subsequently, grand-kids. Which means you'd be alive and free to go kill him again.
And so on, and so forth, to infinity and beyond.
You see that in Kindred. She is pulled back in time to save one of her ancestors, but the question arises, does her ancestor live because she was constantly pulled back in time, or was she pulled back in time because history was changing and she needed to correct it?
There are lots of other books that employ a paradox. Timeline by Michael Crichton (which you can read our review of) is a book that travels back to medieval France. The cast of characters end up interacting with the locals and it's the age old question of, is this happening because I am here or am I here because this is happening.
The Time Traveler's Wife by Audrey Niffenegger also deals with time paradoxes. Henry constantly is jumping from present, to past, to future. The first time that he "jumps" through time, he's a little boy and meets his older self. But we don't find this out until later when his older self "jumps" to the past. But is it the past if he himself is experiencing it? Time really is wibble-wobbly.