i dont think book was a horcrux
coz even if it would have been, and had d snake killed haary even then voldy couldnt have been reborn from d book
coz it was jus a memory
and 1 more thing,if there is gonna b a direct fight betn v and hp then how would they duel?coz they are both havin wands of same bird and hence 1 would oppose d action of others.....