If you are new to technicalcommunication, and what it can do for you; or, if you want something to tell you more about technical communication, here are some books that I recommend:
Ament, Kurt, 2003, Single Sourcing: Building Modular Documentation. William Andrew Publishing
Coe, Marlene, 1996, Human Factors for Technical Communicators, Wiley
Hackos, JoAnn, 1997, Standards for Online Communication. Wiley
Hackos, JoAnn, 2007, Information Development, Wiley
Rockley, Ann. 2003, Managing Enterprise Content, New Riders
Rosenfield & Morville, 1998,Information Architecture for the World Wide Web, O'Reilly
Schriver, Karen. 1997, Dynamics of Document Design. Wiley
Wurman, Richard Saul, 2001, Information Anxiety 2, Que Books
Style Guides
Style guides are the technical communicators best friend. So much technical writing has so many inconsistencies that the reader is confused. I use the following style guides all the time, because most clients have no in-house style guide.
Sun Microsystems Inc. 2003. Read Me First! A Style Guide for the Computer Industry. Prentice Hall PTR. ISBN 0-13-142899-3.
IBM Press, 2004, Developing Quality Technical Information. A Handbook for Writers and Editors, Prentice Hall. ISBN 0-13-147749-8.
Microsoft. 2004, Manual of Style for Technical Publications. Third Edition. Microsoft Books
Alred, G J et al, 2003 Handbook of Technical Writing, St Martin's Press, New York, ISBN 0-312-39323-7.
You may not like all the conventions in these books. You can write your own style guide as you go. I recommend these guides as a good starting point.