We know the best Book we have is the Bible, which has everything for life that we need to live a perfect life. I would like to know should we stop with Bible and Books that are based on Bible, or may Christians read non-Bible based books that teach good things such as "The Power of positive thinking" etc. They seems harmless written by well known authors like Dale Carnegie, Norman Vincent Peale etc.
This is opinion only, but I'll throw my two cents in. I'm also not going to add in supporting Bible verses as I'll stick to commonly accepted, cross-denominational concepts that any Christian should be familiar with. (If comments ask for verses, I will come back and edit them in.)
Most of the self-help books that I've read personally are, in retrospect, based on very humanistic concepts, or the popular psychology of the day. However, many of them contain very good ideas mixed in with the psychobabble.
My personal opinion is that there is nothing inherently wrong with reading self-help books, provided that you've got a solid foundation in Biblical doctrine, and are able to discern the good from the concepts that are anti-Biblical.
Many of these books have value, and follow along with Christian teachings. Books on success often advocate following the golden rule - treating your peers, employees, customers, etc, as you'd like to be treated. Or the teach the value of honesty, integrity, etc. None of these are anti-Christian, and all are examples of how God would have us behave anyway.
The biggest pitfall that I an see with these books is that they can further the illusion among the unsaved that following the advice in the books makes them a "good person". Of course, a person has to realize that he or she is lost before they can turn to the Savior for salvation. We can all be better people, but we can never be good enough to earn our own salvation. (If we could, the Cross would not have been necessary.)
Then there are the books that teach outright contradictions to the word of God. Humanistic, or spiritual growth books that point to one new age theology or another. Again, these can be dangerous for obvious reasons. However, I still believe that someone with a grounding in doctrine with the gift of discernment can still read these books and use the knowledge for God's will. the people who fall for these lies need the Savior just as much as anyone else, and you can't refute something you don't know about.
As a parallel to this last once, many Christians study the beliefs of various cults and non-Christian religions in order to learn how to more effectively witness to those involved. It helps to provide a common starting point. Being aware of what's being taught in these "new-agey" books can be valuable for the same purpose.
The bottom line comes down to whether or not you're grounded enough in the Word to understand and discern the truth from the lie.
Sure, we may read them. (1 Corinthians 10:23)
But really, why read a productivity self-help book when The Ultimate Productivity blog says it all? And which is a better use of time: reading self-help books on becoming a better person, or actually helping the needy like the Bible tells us to? (James 1:27)
Self-help was suggested to Jesus in the moment of crucifixion.
Jesus chose to help others instead.
Mark 15:29-30 (ESV)
29 And those who passed by derided him, wagging their heads and saying, "Aha! You who would destroy the temple and rebuild it in three days, 30 save yourself, and come down from the cross!"
I'm going to come from a different perspective.
Summary: You can read whatever you want, provided it doesn't take you away from God.
The problem with saying "All X is bad" is that not everything can be categorized as either "bad" or "good". Also, we, as Christians, basically have the right to do whatever we want, provided that God permits us:
1 Corinthians 10:23 (NIV)
“I have the right to do anything,” you say—but not everything is beneficial. “I have the right to do anything”—but not everything is constructive.
So then the question is: Does God permit us to read X?
In General, yes!
However, we have to make sure to try to have a pure heart--a heart for God. If a book is going to draw us away from God, we should leave it alone. Otherwise, it will be fine.
I'm sure that the book Pleasuring: The Secrets of Sexual Satisfaction is a fine book. (I couldn't say on my own authority, I haven't read it!) However, if you have problems with lust, that's probably not the book for you. However, in the confines of marriage where lust is not a problem, this book can be helpful and instructional.
Ultimately, we just have to make sure that if we do anything, it brings glory to God. Avoid the books that will pull you away from God (whether Self-Help, Fiction, or Historical) and focus on the books that will actually help you out!
Another side note is that there are actually Christian self-help books out there. Boundaries for kids is an excellent book to help parents learn to raise children and it is written by two Christians and from a Christian perspective (although not explicitly a "Christian" book).