Absolutely Beautiful
I used to go to Lassen as a child, but have re-fallen in love with it as an adult, heading back with my children. About a million times less crowded than Yosemite and just as beautiful, Lassen does not disappoint.
Similarly, the campground at Manzanita Lake is miles above any similar campground in the centrally located parts of Yosemite (though outer campgrounds in Yosemite can be nice).
Plenty of space, good prices, beautiful trees and most of all an absolutely beautiful lake all make this campground a winner. Pretty much all of the campgrounds in Lassen are great, but this one has the benefit of being one of the larger ones, so it's (when we were there) easier to find a good spot without reservations. Can't wait to head back.