When I sync it wants to remove my library of previously purchased items?

Here's the back story, my HP laptop bit the dust. So I got a MacBook Pro(LOVE IT!)

Here's the issue at hand

When I go to sync my iPhone 5 and transfer some larger files to save space, it's trying to say to sync it up it'll remove my library of purchases, photos, etc. NOT what I wanted... I just want to transfer my audiobook... that's it!