Both the Amazon and the B&N links work fine for me both on your site and on LJ. They both get me to a page listing all of your eBooks, no redirection to te front page of the site. Of course, that's with JavaScript blocked, it's quite possibl;e that B&N have some tricksy JS which notices that it was referred from LJ and disallows the search (they may have been burnt by "deep linking" from LJ posts before).

Many sites disallow "deep linking" (i.e. to anything apart from the places they want you to enter the site) altogether, because they want to be able to move things around without causing broken links. Or only allow it via special links (so, for instance, they might allow an author to create special links to their books which would then be independent from the actual links, much like using tinyurl hides the destinationlink).