As I'm writing my post I've noticed what I think is a nice way of linking to books. It is to use the wikipedia ISBN [book sources](http://en.wikipedia.org/wiki/Wikipedia:Book_sources) link like [this](http://en.wikipedia.org/wiki/Special:BookSources/019850294X#Online_text), whose target is:

`http://en.wikipedia.org/wiki/Special:BookSources/019850294X#Online_text`

The general format is:

`http://en.wikipedia.org/wiki/Special:BookSources/ISBN#Online_text`

What I like about this is that the user is then automatically provided with links out to any of their favorite sources for books. For example if you're a library user you can link out to WorldCat and get to your library in a couple of clicks. If you want to take a look at the Google books entry or buy on Amazon those are there too...among too many others to mention. The only downside of this is that the user always has to click at least twice, but I think the generality and stability of these links might be worth it.

I included this and the doi linking idea on the [How to](http://www.azimuthproject.org/azimuth/show/How+to#References) page. Feel free to edit/remove/suggest alternatives.