There are a total of 5 books in the Bible that only contain one chapter: 1 in the Old Testament and 4 in the New Testament.

The Old Testament:

• Obadiah

The New Testament:

• Philemon
• 2 John
• 3 John 
• Jude

Our most popular navigation type (how the table of contents are displayed) is called "3-Tap". It's called this because you simply tap 3 times to navigate to a Book, Chapter, and Verse. 

The only exception for 3-Tap are the one-chapter books. This single chapter books are treated as "two taps". The list of chapters are skipped, since there's only one, and the user is immediately brought to a list of verses.