Complex sentence: The inventory for its retail and online sales is over four million new, used, rare, and out-of-print books; since 2005, its website has also offered DVDs with free shipping, with an inventory of over 40,000.
Split into simpler sentences: The inventory for its retail and online sales is over four million new, used, rare, and out-of-print books. Since 2005, its website has also offered DVDs with free shipping, with an inventory of over 40,000.