don't waste it!
suggestions - some places give you gifts if you sign up. i got a really nice gift certificate once that way . i think uptodate used to do that.
or buy some books, read them then sell them. if they are in great condition (don't write on them) you can usually get money for them.
just do a google search for places that buy used medical books, and make sure the ones you buy they want. for example
Sell Textbooks For Cash - Sell Used Books | Cash4Books
BTW there are a lot of these online, even amazon will buy books.