Alpaca Field Manual   by C. Norman Evans DVM   (Excellent book....if you only get one it should be this!)

Medicine and Surgery of South American Camelids   by Murray E. Fowler, DVM  (get this one for your vet)

Llama and Alpaca Neonatal Care   By Brad Smith, Karen Timm and Patrick Long     ( keep this one in  the barn during birthing season)

The Alpaca Book   by Eric Hoffman and Murray E. Fowler DVM   ( lots of good information covering many aspects of alpacas)

Caring For Llamas and Alpacas - A health Management Guide     by Claire Hoffman DVM

The Camelid Companion - By MartyMcGee Bennett   A great resource for handling , training and enjoying your alpacas
 

The Reproductive Process of South American Camelids   by P. Walter Bravo

Most of these books are available at  http://www.useful-items.com