I know very few readers who would turn away a "pre-read" novel. Many used book stores offer trade credit so you can trade in your old books for new ones. I can't tell you how many mint condition books I've found just scouring the shelves, especially in YA sections. Check the Indie Bound store locator for used bookstores near you.
The Buy N Trade
For example, our used book store won't accept hardcover over-sized books if a paperback is already out. Either way this has the potential to be low-reward so don't get books you won't mind keeping.
Buy In Pairs = Free Shipping
booksamillion.com, BN.com and even Amazon offer free shipping on most books, when you spend 25$ or more. Take advantage of this when you want those shiny hardcover new releases. Find two new releases and purchase them together to save you money on shipping
Waiting on Wedensday you can see upcoming books far in advance. If you pre-order online you can recieve a book for a much cheaper price.
For instance, I ordered The Fault In Our Stars by John Green from Amazon in July for 8.99, knowing the book wan't coming out until January. Keep in mind when the website will charge. Barnes and Nobles charges you when it is shipped while Amazon charges straight up.
Changes in Cover Art
Novel covers can sometimes get a makeover and you might find a deal on the old version. Check out bargain sections online or in store for older editions. For examples we found old editions of The Uglies series at Books-A-Million for $3.97
Top Photo via Flickr, Allisa Lemaire