If you're frequently passing by a university library, see if they have a shelf where they sell old books. Mine does, and I've scored some sweet stuff there, e.g

If you're frequently passing by a university library, see if they have a shelf where they sell old books. Mine does, and I've scored some sweet stuff there, e.g. Dunford and Schwartz' Linear Operators Part 1 & 2 together for $8, which looks to be $150 + shipping for used copies from Amazon ($400 new). As you can probably tell, there's an arb opportunity there as well.