How does Allah communicate to the Prophets? Does he communicate through means other than by revealing verses of a holy book? Or is it possible for Him to communicate in other ways? I guess my question could be even more specific. Could God reveal aspects of the unseen to a prophet that was not revealed in a holy book to him?

Salaam, And do not argue with the followers of earlier revelation..."We believe in that which has been bestowed from on high upon us, as well as that which has been bestowed upon you for our God and your God is one and the same, and it is unto Him that we surrender ourselves." The BIGGEST part of Islam is believing in one God and Quran. This verse is saying not to argue with those of earlier revelation since they believe in the same one God and believe in God's (older) revelation. But, we are even closer, we have the same God and the same Quran. In my opinion, I think it is best to lay this to rest (heh...that rhymes). As this verse points out, its not that big a deal in the grand scheme of things, we all surrender "unto Him".