Tom Brown's book, The Tracker has some pretty vivid descriptions of the Pine Barrens. Not a place I would like to be without my OnX.
Its pretty big area, bigger than the actual park too, including private property thats contiguous.
http://www.newjerseyscenic.com/sitebuildercontent/sitebuilderpictures/nj_pinebarrens_map.gifIts a little bit larger than whats shown in the map.
Its not some vast impenetrable swamp that will eat all comers alive. The real issue is that its painfully featureless therefore easy to get turned around. Of course a compass will solve that.
Factor in that you are talking NJ, which is small and isnt particularly crawling with veteran explorers, and it can be a bit troublesome at times.
Vast in comparison to out west, or even PA, it is not though.
Actually quite beautiful, a unique ecosystem in the North east.
I would wager a guess that exposure is a bigger concern. Just walk east and eventually you will hit the Parkway.