Justin Bieber -- This Book Makes Me Thinketh

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.