Hmm, I've never run across a book either. There is, of course, a huge amount of in-depth information on this site, which I trust as a source. But it is not comprehensively organized like a book would be. On the other hand, even though veterinary medicine may not be moving quite as fast as human medicine, any book would quickly be outdated. And might not have had the best information in the first place.
Some additional reading I would recommend:
1) The AAHA and ISFM disease management guidelines, reflecting consensus opinions in veterinary medicine, that are linked from this site's
Health Links page.
2) The material offered on the websites of major vet colleges, e.g.
Cornell's.
3) What the always invaluable
Dr Lisa Pierson has to say.
4) I found some useful material on the
Pet Diabetes Wiki.
5) What
Wikipedia has to say is generally worth a look.
Opinions on the value of these sources may vary.
The FDMB has its own culture with its own way of approaching things. This community is oriented towards very active management of feline diabetes, which is not -- alas -- a universal practice. That said, when in doubt I would always be comfortable posting here, confident that I will get knowledgeable and caring replies (with, of course, some people providing better answers than others). And I don't believe anywhere else offers the board's level of immediate, situational advice.