"The border trilogy first published as a single volume in Everyman's Library in the USA, 1999. Individual volumes originally published by Alfred A. Knopf"--T.p. verso.
All the pretty horses
The crossing
Cities of the plain.
OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
The border trilogy by Cormac McCarthy. ISBN 9780375407932. Published by Alfred A. Knopf in 2008. Publication and catalogue information, links to buy online and reader comments.
