We were (just) at Liberty Glen for one night in December, a Friday night, and there were a total of 4 sites taken of the 96. For reference, we are a couple, a dog, and a short (23') class A RV and we mostly do/prefer dry camping in more picturesque and secluded settings. The B loop was closed for the winter, but still--we had the place to ourselves and the pick of sites. I reserved online about 45 minutes before we arrived, and that posed no problems. You MUST reserve ahead of time online, even if by only minutes, because you need the gate code at the unmanned entry gate, and you get the gate code with your reservation confirmation (the gate code changes regularly).
I read prior reviews about there being no water (still true--host said the Corps of Engineers are trying to fix the pump issue that has apparently knocked out all of the water to the campground; there were very clean porta potties at all of the bathrooms) and about there being no shade (also seemed like it could be an issue if it were hot, because we saw only some sites that would have summer shade). Both of these being said, we really enjoyed the solitude, location, size (it's pretty huge), and otherwise well maintained nature of the campground. The main host, whose name we did not get, was great and knowledgeable about the area. He came by once to check us in, chatted a bit, and later was around doing some odd jobs on his quad.
Now that we've been, we'll definitely go back. If you go, plan to be fully equipped with water and shade (if you go when it's hot).