Classics

• E-book apps that boast thousands of e-books usually contain a collection of classics that are in public domain. This means they can be used freely without the original owner's permission. Most of these books can be found online for free, but the apps have them all in one small package, eliminating the need to search for the titles individually.
  
  

Bibles

• Bibles are all over the App Store, with more being released daily. They can be found in nearly every language. Some features include audio playback, search and the ability to bookmark a location. Some even have a built-in dictionary to easily search for the definition of words without leaving the app.
  
  

Kids

• Children's e-books on an iPod Touch are formatted many different ways. The most simple versions have illustrations and the pages are turned by tapping the screen or a tiny arrow in the corner. The more detailed apps will read the book aloud to your child, play special animations when certain pictures are tapped, or even record his own voice as the narrator.
  
  

Free

• There are numerous free books in the app store, but some of them charge 99 cents for the app then you get the books for "free." The updates come with the purchase, so as more books are released, they can be downloaded to the app. Other apps will let you install their e-reader for free, then make you buy the books through an in-app purchase. Lastly, the truly free e-books will have ads displayed at the bottom to cover the cost.
  
  

Dictionaries

• Some dictionaries in the App Store are small in size, because they require an online connection to use. Others are very large and contain the definitions within the app, so you don't need a wireless signal. A thesaurus is usually included, and some have a built-in audio feature so that you can hear the proper pronunciation.
  
  

Commercial

• These apps are professionally created by well-known companies like Barnes & Noble, Google, Kindle and Stanza. They have a more polished look without the blurriness that can be found in cheaper apps. They usually have some type of bookshelf that keeps your books organized and easy to find. Synchronization is also a common feature that keeps track of where you left off. If you have a Nook, for example, it will sync with the Barnes & Noble app and vice versa.