Computers and Intractability : A Guide to the Theory of Np-Completeness, Paperback by Garey, Michael R.; Johnson, David S., ISBN 0716710455, ISBN-13 9780716710455, Brand New, Free shipping in the US
Classic text for use in grad school back in the 80s. Still no comparable replacements. Consequently, for an old technical text, it still commands a fairly high used book price.