Yes this is the busy time of year. You could try just showing up but I wouldn't
It is recommended you make reservations if you want to stay specifically at Furnace Creek campground. They do sometimes have a few sites available. You can easily plan a spontaneous stay at one of the two NPS campgrounds 1 mile east called Sunset and Texas Springs which are first come first served only.
When we went in early Nov, group sites required reservations and individual sites were first come first serve. Not sure about late Nov. I suggest confirming on the website to be sure.
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