Managing NFS and NIS by Hal Stern, Mike Eisler and Ricardo Labiaga, 2nd Edition, O'Reilly; ISBN 1-56592-510-6. A little Solaris-specific but good at explaining how things work.
A good source for Linux-specific NIS information is the NIS-HOWTO: www.tldp.org/HOWTO/NIS-HOWTO/index.html.
PADL Software Pty Ltd., NIS to LDAP Migration Tools: www.padl.com/OSS/MigrationTools.html.
