If you can locate the author, you might want to
approach him first. It may be the case that the
copyright has in fact reverted to him. If not,
he might be sufficiently interested keeping the
book "alive" to attempt to reclaim the rights
from the publisher. I seem to remember hearing
of several cases in which copyrights for out-of-print
books were returned to the author at his request.
I would imagine that a publisher would be more
inclined to do a favor for an author than a random
hobbyist.
--Bill