I think it is a very good book. It is hard to explain so I'll type the blurb from the back of the book:

"Roy and his cousin Danny are a couple of serious computer geeks"(I don't have anything against comp. geeks,I am one)
"They've played tons of games and have 'surfed' all around the world on the net.
One day they discover a mysterious E-mail from some guy named Vlad.Roy's instincts tell him to delete the message and forget about it. But Danny can't resist.He enters the password, and suddenly the boys are involved in a terrifying on-line game called the Monster Mash.
Little do they know that they'll end up playing for their lives!"
[Dum Dum Dummm]