Rachel P has given a great review of the individual campsites; i have nothing to add to that! It's a rustic/no frills campground with vault toilets. This area is definitely a great spot to view moose or go fishing. It is also near Umbagog National Wildlife Refuge where you can view moose and loons galore! I've enjoyed kayaking and photography there. 

There are a mixture of sunny and shady sites, most along the river itself. The more open ones are better suited to RV/trailers. Scout out the ones at the very end before you drive down to 42. Kayaks and canoes are available for rental.

Beware! Google will direct you to a closed entrance to the park! If you're coming from Errol, you'll be fine, you'll see the main entrance before the closed one; If you're coming from the south, then continue past the first entrance and you'll reach the main one. i was here in October and it was COLD, so be prepared for all kinds of weather.