Amazon
will sell you a new or used copy for less than what the publisher
charges.
You can find the original edition cheaply used at
www.abebooks.com.
It will probably do.
Kent Beck, Cynthia Andres,
Extreme Programming Explained, Addison
Wesley 2nd Edition. ISBN: 0201616416.
This is a $38 paperback - not expensive for a CS book, but still
pretty steep. You can find used copies on the web for about $5. And
even the first edition will probably do.