function theme_amazon_block($selected_book) questions

I've been hacking away at this function in amazon.module, in attempts to get this random block to link to the node, rather than jump to the amazon.com website.

I commented out both the 'if ($is_review) statement' and the 'else' values. This does change the link to the node, except it can't seem to determine the node, which I don't understand. Isn't each amazon item stored as a node, as in 'if (isset($selected_book->nid))' should be true all the time?

Can anyone clear this up for me? Essentially I always want this random image to point to the local node, and never to the amazon website.

Brad