Additional GET variables with RewriteRule

Howdy everyone,

I am trying to get my RewriteRules working compeltely.

Right now I have this:

RewriteRule ^([a-zA-Z0-9]+)$ $1.php
RewriteRule ^([a-zA-Z0-9]+)/$ $1.php

That works fine. As does this:

RewriteRule ^books/wanted$ books.php?category=wanted
RewriteRule ^books/wanted/$ books.php?category=wanted
RewriteRule ^books/unwanted$ books.php?category=unwanted
RewriteRule ^books/unwanted/$ books.php?category=unwanted
RewriteRule ^books/all$ books.php?category=all
RewriteRule ^books/all/$ books.php?category=all

However, if I navigation to books/all/?some_other_variable=wtf it doesn’t work - $_GET[“some_other_variable”] doesn’t exist.

Any help here would be much appreciated.