Is it ok to believe in some parts of the bible and not others or is it all or nothing?

Given that the Book is not internally consistent (flatly contradicts itself at some points), it's not possible to believe in all of it literally. I read the OT as Parables a lot of the time, and never crack my Bible without prayer, asking the Spirit for guidance. There was another Teacher who used parables to get His point across at times - couldn't He have learned that technique at His Father's knee?

Life is never that simple. There are a wide range of beliefs, from those who are convinced that it can be taken literally to those who consider it to be one great series of allegories with some historical tradition thrown in and a whole range of differing interpretations along the way. Not to forget that the devil can quote scripture for his own purpose. 

People have argued over whether whether God, or gods exist or not since time immemorial. Believers have argued over who/what that being(s) is/are and what, if any, writings are holy. People have argued over the interpretation of the writings they mutually agree are holy.

The Bible, or portions of it, are holy books in Judaism, Islam, and Christianity. Under each of those labels exist a wide range of beliefs. In my experience, no two people have completely agreed on any interpretation, even those who are members of a particular denomination or sect of a particular religion, and may even sit in the same house of worship weekly.

The Bible is a collection of books which contain history, law, poetry, parables, letters, etc. It should be taken in context as to what is being read, and to whom it applies. Given the time period it was written in and that it was written in ancient languages, that's not always easy to do, hence the reason even scholars spend a lifetime studying it.

Faith is personal, and each of us must decide what to believe for ourselves. People have always argued the subject and will continue to do so as long as there is no definitive proof for all to see and comprehend. If the athiests are correct, we simply die. If those of us of faith are correct, though, I suspect we'll find out that not a single one of us got it exactly right.

As always...JMHO.