What kind of content makes for a good free eBook app? Aside from eReader apps like iBooks, Kindle, Nook and Google Books, comics and weird fact book also ruled our Top 20 Free Book Apps list.

DC Comics, Marvel Comics and Comics all ranked high on the Top 20 Free Book Apps list this week from the Apple App Store. At the same time, Weird Facts 1000 (pictured), Love Quotes 500, Sex-Facts 500 and Dirty Sex Jokes all made the Top 20.

If you want to learn more about this growing side of the the publishing industry, check out Mediabistro’s upcoming Publishing App Expo on December 7-8. Speakers include author John Green and executives from Barnes & Noble, Zinio and ComiXology.