I'm a librarian by training. (So I'm a self-taught coder - which maybe explains a lot of lameish posts :) )
Anyways, if I'm referring to a book in a post, I'll always link to further info - some sort of authorative source about the title, that preferably adds value. Most Library Catalog records do not add much value imho - only basic bibliographic description e.g. Library of Congress full record for the Camel (This url might break as it includes a kind of pid)
Now I could be wrong but Amazon probably adds the most value, (in terms of the most reviews, sample chapters, recommendations etc, but I can't link there 'cos of the patents issue. Accordingly, I link to fatbrain.com.
If anyone has a better compromise, I'd appreciate learning about it.