Until the 1990s, there were very few instructional SM books around. Now you can find them almost anywhere, especially online. This is not a definitive list, just my thoughts on excellent SM-oriented books. I haven't seen any recent books to add to this list, hence virtually all titles are from the mid 1990s to 2000 or so.
The Master's Manual by Jack Rinella, Daedalus Publishing, 1994. ISBN 1-881943-03-8.
Miss Abernathy's Concise Slave Training Manual by Christina Abernathy, Greenery Press, 1998. ISBN 9-9639763-9-7.
The Sexually Dominant Woman: A Workbook for Nervous Beginners by Lady Green, Greenery Press, 1998. ISBN 1-8901591-1-5.
The New Bottoming Book by Easton & Hardy, Greenery Press, 2001. ISBN 1-89015935-2.
Consensual Sadomasochism: How To Talk About It and Do It Safely by William A. Henkin, Ph.D. & Sybil Holliday, CCSSE, Daedalus Publishing, 1996 ISBN 1881943127.
Erotic Bondage Handbook by Jay Wiseman, Greenery Press, 2000. ISBN 1-890159-13-1.
The Lesbian S/M Safety Manual by Pat Califia, Lace Publications, 1988. ISBN 1-55583-301-2 (book is now out of print).
The Loving Dominant by John Warren, Greenery Press, 2008. ISBN 189015-972-7.
Screw the Roses, Send Me the Thorns by Philip Miller & Molly Devon, Mystic Rose Books, 1995. ISBN 0-9645960-0-8.
SM 101 by Jay Wiseman, Greenery Press, 1998 ISBN 0-9739763-8-9.
The New Topping Book by Easton & Hardy, Greenery Press, 2003. ISBN 1-890159-36-0.
Coming to Power and The Second Coming are currently out of print.
Coming to Power: Writings and Graphics on Lesbian S/M by Samois. Alyson Publications, 1987. ISBN 0-932870-28-7
LeatherFolk by Mark Thompson, Daedalus Publishing, 2004. ISBN 1-88194-320-8.
Leather Sex: A Guide for the Curious Outsider and the Serious Player by Joseph Bean, Daedalus Publishing, 1994. ISBN 1-8819430-5-4.
The Second Coming by Pat Califia & Robin Sweeney, Alyson Publications, 1996. ISBN 1-55583-281-4.
Most of these books (with the exception of out of print titles) can also be ordered through Amazon.com or Good Vibrations.
Out of print books listed may be found by going to either Harvest Book Company or Abebooks and doing a search.