I'm strongly opposed to any attempt to create a 'real'
Necronomicon since no book could ever come close to being as maddeningly evil as the work described by HPL and other Mythos authors.
The closest thing I can think of in terms of genuinely feeling like a book of 'forbidden knowledge' is
Cyclonopedia, which I started a thread about (
http://hppodcraft.com/forums/index.php?topic=1299.0) - it's had plenty of views but no-one's yet replied, so I can safely assumed no-one's read it. It's well worth checking out if you don't mind tackling a 'challenging' read. Also it's all about the Middle East, which ties it in nicely with Abdul Alhazred and his original
al-Azif.