Justin Bieber has been doing a lot of pondering ... so his choice of book makes it appear.
Bieber was in Beverly Hills Friday clutching "As a Man Thinketh" ... an essay from 1902 by James Allen that many consider a very helpful personal development tool.
The book stresses the importance of your own thoughts ... and how they can effect your personal life. Think "The Secret" ... but much older.
Sounds like recommended reading.