This topic from Long and Short Reviews was a surprisingly tricky one. I read voraciously, but don't always have time to re-read even if I want to. However, when checking my Kindle, I did find a few that I faithfully re-read because they never, ever get old.
Royal Blood - Bertram Fields. This book is what made me a Ricardian, and it's always fascinating to dip back into it and remind myself why Richard III interested me so much.
This Is Going To Hurt - Adam Kay. This book and its sequel "Twas The Nightshift Before Christmas" are an absolutely hilarious take on being a junior doctor. How that man managed to keep a straight face through some of these incidents is beyond me.
The Wilder Life - Wendy McClure. Wendy McClure travels America following Laura Ingalls Wilder's life, and it makes for an amazing read.
So what do you re-read or want to re-read?