We had origially reserved a site in the A loop, but we didn't like that one so we drove around the first-come, first-serve loops in hopes of finding a better site. We finally settled on D-30, which seemed to be the best available site in the tents-only D loop. The site was quieter because it's on the edge of the campground and the Manzanita Creek Trail was right by the campsite. We asked a ranger how to "switch" our registration and we were told to just take the sign down from our reserved site and hang it on the post at our new site.
Manzanita Lake is one of the nicest and best-run campgrounds we have ever camped in. The restrooms were modern and clean, there is a cool store nearby where you can buy everything you need, there are laundry and shower facilities, and Manzanita Lake is a short walk away. There is also a visitor center nearby with interesting displays and ranger-guided hikes and activities. We also rented kayaks and took them out on Manzanita Lake, which was a blast and where we got our first good look at Lassen Peak. There is a trail which leads from the campground along the south side of the lake and where you can get a great view of Lassen Peak at sunset from the west shore of the lake.
One of the great features of this campground is that two of the loops are on the NRRS reservation system and the other two loops are first-come, first-serve, so you have the best of both worlds. We were there in Aug. and found that this campground really fills up on weekends and empties out during the week. The least full nites are probably going to be Sun., Mon., and Tues. There are also campfire programs on Fri. and Sat. nites.
The only drawback of this campground is that it's a long drive to the south end of the park, about an hour to the south entrance. This campground is overall a winner. See my separate review of Lassen Volcanic National Park for more info.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.