The two main publications on agave are Berger, A. 1915, "Die Agaven. Beiträge zu einer monographie" [The Agaves. Contributions to a monograpy"], Verlag Gustav Fischer, Jena, Germany (Reprint: Gustav Fischer Verlag, Jena, Germany, 1988) and Gentry, H.S. 1982 "Agaves of Continental North America" The University of Arizona Press, Tucson, Arizona, USA. Bergers book is an incredible accomplishment when one realises that it was published in 1915, and Berger never having left Europe.
See the pages next to this one for lists of literature I have found on agaves, and for booksellers on the web. ("Succulenta" is bulletin of the Dutch/Flemish cactus and succulent society.)
Pages Main and Special are updated about every two months. For the most recent files see AgaveData > Literature.
I have found untill now these sites with extensive information on literature about agaves:
http://www.users.globalnet.co.uk/~jankol
http://home.eunet.no/~finnerwa/agave.html
Succulent plant booksellers:
http://cactus-books.com/index.html
Search machine (that immediately produced Gentry):
http://www.addall.com/
Please send me more information if you have so at AgaveWeb !

Agave wocomahi (habitat picture)
(Copyright Starr Nursery, see page Plants and seed)