The holiday shopping season is upon us, and once again e-book readers promise to be a very popular gift. Last year’s holiday season saw ownership of a dedicated e-reader device spike to nearly 1 in 5 Americans, and that number is poised to go even higher. But if you’re in the market for an e-reader this year, or for e-books to read on one that you already own, you might want to know who’s keeping an eye on your searching, shopping, and reading habits.