Do you own multiple copies of any books? Why? Is it the format? Size? Just because you love it?
Don’t forget to leave a link to your actual response (so people don’t have to go searching for it) in the comments—or if you prefer, leave your answers in the comments themselves!
Booking Through Thursday 
Oh yes! https://tbrtuesday.wordpress.com/2016/02/04/booking-through-thursday-multiples/
I have…a lot of Bibles. They’re popular gifts if you grow up in a very religious subculture like I did. As an adult, I’ve looked for different versions for comparison (Orthodox vs Catholic vs protestant), so I’ve added to the collection.
Beyond that, I have two copies of The Rainmaker because my paperback is so battered from re-reads I know it’s only a matter of time before it surrenders to the inevitable.
The only other duplicates I have come from buying a box of books (Asimov and Star Trek) that had the odd piece in them that I already owned. I give those away, though.
https://geekishbooks.wordpress.com/2016/02/06/booking-through-thursday-5/
http://dawntreader-island2.blogspot.se/2016/02/multiples-btt.html
Great question!
http://www.kwizgiver.com/2016/02/booking-through-thursday_11.html