[OT] The Kindle and the paper book

I just got an Amazon Kindle, and think its fantastic. However, I’m now torn on what to do with 1 particular book;  Infinite Jest by David Foster Wallace.  The reason is that its a massive book (1100 pages) and I am on page 20.  Should I re-purchase it on the Kindle? The Kindle seems ideal for it, yet I don’t want to spend another $10 on a book I already own.  If I don’t, I doubt I’ll actually get to finish it as I have very little time to read outside riding the train, and the book is just too big to carry around.  Plus, I have 12+ hours of train time coming up this week . . .