The single best book on the goth movement is "Goth: Identity, Style and 
Subculture," by Paul Hodkinson (Berg Publishers, 2002).  Written from an 
academic perspective, it explores the identities, practices and values 
of the goth scene, and examines how it fits in with the rest of society.  
It's not a modern guide to goth, but instead provides a complete 
ethnographic study.

"Music to Die For" (Cherry Red Books, 2009) is the latest guide to the 
scene by Mick Mercer.  Taking an international view, it provides an 
extensive guide to goth-related bands, and is complete with 
discographies, line-ups and contributions from many of the groups 
themselves.  This is Mick Mercer's fifth book on goth, and the one most 
relevant to today's scene.

"The Goth Bible: A Compendium for the Darkly Inclined" (Saint Martin's 
Press, 2004) is a passionate examination of the goth scene by Nancy 
Kilpatrick.  Ninety-five goths contribute quotes and opinions as the 
book provides an insight into the past, present and potential future of 
the movement; as the work progresses it covers subjects as diverse as 
absinthe, architecture, club culture, fashion, gardening and marriage.

"What is Goth?" (Red Wheel/Weiser, 2004) is a humorous goth-spotting 
field guide.  It was written by Voltaire, author of the "Oh My Goth!" 
comic book series.  Within its pages you will also find advice on 
finding your goth name, how to generate a gothic poem, and how to 
accomplish difficult dance floor manoeuvres such as "pulling the evil 
taffy."  "Paint It Black: A Guide to Gothic Homemaking" (Weiser Books, 
2005) is the similiarly tongue-in-cheek follow-up.

"Goth Chic: A Connoisseur's Guide to Dark Culture" by Gavin Baddeley 
(Plexus Publishing, 2002) is another attempt at exploring gothic 
culture.  It has a much wider view of what goth constitutes, covering 
everything from horror comics to vampire cultists.  Although quite 
interesting it's not as relevant as the writings of Paul Hodkinson, 
Nancy Kilpatrick or Mick Mercer.

"The Dark Reign of Gothic Rock: In The Reptile House with The Sisters of 
Mercy, Bauhaus and The Cure" (Helter Skelter Publishing, 2002) by Dave 
Thompson gives a good insight into the history of gothic rock, although 
it's only indirectly relevant to the present movement.