A good introduction to stellar
spectroscopy appeared in the October 1996 issue of Sky &
Telescope magazine on pages 48-51. The article includes an
excellent set of reference spectra. A version of this article can be seen at http://www.skyandtelescope.com/howto/basics/3305876.html. Also see the September 2000 issue,
pages 38-44 and the August 2004 issue, pages 44-49.
The best book on this subject is
"Stars and Their Spectra" by James B. Kaler, Cambridge University
Press. It is
available through Willman-Bell, Inc. See Willman-Bell's monthly ad in Sky
& Telescope or go to www.willbell.com.
The Peterson Field Guides, "Stars
and Planets", Fourth Edition,
by Jay M. Pasachoff, contains a set of star maps that are useful with a
spectroscope. Stars to sixth magnitude are color coded according to
"A Spectroscopic Atlas of Bright Stars", A Pocket Field Guide, by Jack Martin.
Published by www.springer.com.