The Bathroom Reader's Institute currently comes out with a variety of books for your bathroom pleasure...
There are currently 17 editions of the main Bathroom Reader series published, with one being published every year. These books have all sorts of trivia embedded in them, whether it be the story of Saturday Night Live or the origin of the bra, all of the stories are well-written and keep your attention for a while.
They have also published their second edition of Bathroom Reader: For Kids Only, a more kid-oriented edition of the books with more facts that they'd find interesting. This year they'll be adding another specialty book, the "Bathtub Reader for Moms", conveniently coming out around Mother's Day.
There are also two puzzle books that they've published, which are the typical crossword and acrostic-type fare, only using the facts and themes from their books to give them an added trivia boost.
Then there's the "Bathroom Reader Plunges Into" series... basically the same idea, with random stories and trivia, only focused on certain themes. Currently, the BRI has plunged into "Great Lives", "The Universe", and "History", all with similar results.
One of the tenets of Bathroom Reader's philosophy is that they'll accept material from anyone in their next book. If they really like the material you send them, they'll send you a copy of their next edition for free!
And no, you don't HAVE to read it in the bathroom. But it's the most interesting bathroom reading you'll ever get.