Walden. I've read it a handful of times. Love it.
Desert Solitude, by Ed Abbey. My favorite book of all time. I reread every few years.
From my youth. They still hold up so well…
Starship Troopers (I know; very different from Walden)
Most anything by Jack London or Maupassant or Poe or Lovecraft
Recent reread:
The Road, by Cormac McCarthy. Just so incredibly good.