Why has my recently bought peanut butter such a liquid consistency?
What you can see in the jar is peanut oil, which has separated and floats on top. It means, you have bought a non-homogenized product, possibly an "all-natural" or "organic" product.

Just stir the oil into the thick paste at the bottom and use as usual. 

For a discussion on how to best achieve this, see What's the most effective way to mix a jar of natural peanut butter?.