The best deals usually come from trade presses, but a few university presses also offer display books at up to 50% off the retail price. MacMillan was selling books for $3.00. Penguin was selling hardbacks at 2 for $10.00. New York University Press was offering hardbacks for $10.00 and paperbacks for $5.00. Sunday morning at the AHA is definitely a great time to build your history library, as long as you can fit all the books into your suitcase.
I only bought two books during my wanderings in the exhibit hall--both from the Penguin table. For $10.00 I got a copy of Kevin Phillips's 1775: A Good Year for a Revolution and Clinton Heylin's E Street Shuffle: The Glory Days of Bruce Springsteen and the E Street Band.
Since Messiah College gave me an iPad I have been trying to think of creative ways to use it. When I see a book in the exhibit that I want to read, but do not want to purchase yet, I take a picture of the cover and add it to my wish list when I get home. This is a lot quicker than trying to write down or "type in" the names of titles while trying to navigate the crowded booths. You should try it. I imagine it is a lot easier with an iPhone than an iPad.
For example, here is Eliga Gould's new book, Among the Powers of the Earth: The American Revolution and the Making of a New World Empire.