Devil's Den is a gorgeous parked tucked in the mountains of Arkansas.  The primary campground for RVs is one of the better campgrounds I have seen.  The facilities and amenities have been great.  The sites are generally spacious.  If you want the best experience - grab one of the sites along the ridge (83, 85, 87) - these have a great view off the back and offer incredible space.  There are several hiking trails within the park and other activities during warmer months (i.e. pool).  If you have a large rig - make sure to take the West Fork exit off I-49 vs. the south exit (Winslow).  There's no cell service whatsoever but Wifi (paid) is offered by the park.  Make sure to stock up on supplies beforehand - there are not many options within that area as far as food and services.