Quickie: Only show Drupal's "Book Navigation" block on Book pages:

1) Go to admin/build/block/configure/book/0
2) "Page specific visibility settings" -> "Show if the following PHP code returns TRUE (PHP-mode, experts only)."
3) Insert the following:

<span style="color: #000000"><span style="color: #0000BB">&lt;?php<br>$is_book</span><span style="color: #007700">=</span><span style="color: #0000BB">db_result</span><span style="color: #007700">(</span><span style="color: #0000BB">db_query</span><span style="color: #007700">(</span><span style="color: #DD0000">'select 1 from {book} where nid=%d'</span><span style="color: #007700">,</span><span style="color: #0000BB">arg</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">)));<br>return </span><span style="color: #0000BB">$is_book</span><span style="color: #007700">;<br></span><span style="color: #0000BB">?&gt;</span></span>