i am also totally getting in to the amazon trade in thing for all my text books. i may make a little more selling the books, but there is less hassle with amazon's free shipping labels and i'll use the gift cards/credit. one of the first books i traded was worth 25.12 in amazon gift card. another worth 32.60. they are starting to add up!
my books are the hardest to pare down, but i take some comfort in my kindle for those i can replace electronically. problem is that so many of my books are not available for kindle. and i still like the feel of the book in my hand! but, being able to search an entire book for text and digitally highlight is a plus. :) not to mention the physical space it doesn't take...i just have to learn to quit trying to use it as a touch screen.