Hannah Higgins' book is very interesting, particularly to shed some light on a non Maciunas-centered vision of Fluxus. Yet, it's probably not the best introductory book for a beginner, who would need first a general overview, as could be obtained from Thomas Kellein's "Fluxus " (Thames and Hudson, 1995), good also for the images, and, for a variety of theorical approaches, "The Fluxus Reader" edited by Ken Friedman (Academy Editions, 1999)
For more advanced fluXists, all these books are highly recommended:
"Mr. Fluxus - A collective portrait of George Maciunas" (Thames and Hudson, 1997) edited by the late Emmett Williams and Ann Noel - you get an in-depth biography of Maciunas assembled as a puzzle from contributions by various artists and friends
"Fluxus Codex" by Jon Hendricks (Harry Abrams, 1988) , though I always found its reference system unnecessarily mechanic, cold and complicated, it is the "bible" of Fluxus for its sheer volume, worth to get for the many illustrations alone
"Critical Mass - Happenings, Fluxus, Performance, Intermedia and Rutgers University 1958-1972" edited by Geoffrey Hendricks, what happens when Fluxus goes to college, very accurate report of a unique experience
etc etc etc
some of these books may be out of print, but I hope you live next to a good public library... happy reading!
Thanks for adding to my list Luc, another fluxbook that I quite enjoyed recently is "The Dream of Fluxus - George Maciunas an Artist's Biography" (Edition Hansjorg Mayer, 2007), this is the catalogue of the first major Maciunas solo exhibition ever, that was held last year in Germany to commemorate 30 years from his death. The book is still available in a English and in a German text version, at a very convenient price if you get it from Amazon. The text is a bit too "detached" for my taste, but gives interesting information here and there, and the photos are of top quality (check Maciunas' strip tease sequence in drag!), a very recommended piece in the puzzle to complete the portrait of the ever intriguing Maciunas dramatis personae...
Tanja,
you find some of the books on Fluxus mentioned above in this discussion simply on Amazon or other booksellers on the web, they are not very expensive books and surely worth the money!