The best way to get a book that's checked out is to request a copy from another library where it's available. The first thing to do is try to request it from Bowdoin or Colby. The steps for that can be found here.
If you still haven't found an available copy after trying all of the above places then you can request it from interlibrary loan. Click on the Account link just above the search box on the library home page. Then click on Interlibrary Loan Login to make a new request.