Something for everyone
Lovely wooded campground where you can swim, hike, kayak, bike, canoe, fish, boulder, geocache and explore to your heart's content. Generally large and level sites, many with water access, Make your reservation well in advance if you're planning to visit during peak season or if you want a prime waterfront site. Sites on Horse Island will cost you $5 more than those on Big Island, but many of the sites are directly on the water, making it easy to slip your boat into the lake from your site. There's a campers only boat launch on Horse Island. Much of the lake is better suited to paddle craft rather than motor boats due to it's shallow nature and rocks. The an expansive beach as well, a camp store and boat rentals.
I've had a weekend when my neighbors were playing loud music all afternoon and stumbled drunk through my campsite after dark and other weekends when it was hard to tell there was anyone around.
Driving around this past weekend I did notice that some of the sites had damp spots; site 71 was the worst with deep mud on the long approach. Site 73 is near the bath house, but it has a long approach that provides a little privacy and it's higher than the surrounding sites with water access. Sites in the 3-15 range are waterfront, but they're higher off the water. Site 43-45 are great. Those along the southern edge of Horse Island offer a more level entry. Roads are narrow and many of the site entrances are narrow with rock/tree obstructions in places that may make backing in more of a challenge to thsoe with trailers or RVs. No hookups.
The bath houses are tired, but they offer free showers. Would love to see them renovated and brightened up. Big Island also has cabins available. Phone coverage is poor (Verizon); can usually get texts out. If you want to geocache, download the info for offline use!
If you are used to camping with pets, you'll need to visit outside of peak season as they are not allowed in the campground Memorial Day to Columbus Day and never on the beach.
It has a longer season than many campgrounds in New Hampshire, running to the end of October, and you can generally get a site last minute if you're waiting on the weather and don't need/want a water site. Its proximity to Boston makes it great for a quick getaway.