Take a photo of a barcode or cover
wctracy 's review for:
The End of Eternity
by Isaac Asimov
I though this was a great concept for a story, especially having read a lot of time travel stories. It gets into some of the underlying questions of what happens when you start changing time, and even provides a pretty good answer. If you've read the Foundation books, you can see some of the connection here that Asimov created later in his life.