First, is Islam a way of life or not?Anyone who believes Islam is contained within one book obviously knows little about Islam.
Second, sure there are some Muslims (and Christians) that do not look at the book as the sole (or primary) source of doctrine. But that is more a reflection of the character of their particular denomination, age being a highly significant factor. As a religion ages, it incorporates all kinds of new traditions, doctrines, rituals, etc.
Which is why a denomination like Catholicism for example, as you say, relies on the Pope's decrees etc... its old and stuff gets tacked on to the religion over time... While a denomination like the Jehovah's Witnesses, which is very young (in religious terms) pretty much sticks to the text of the Bible and the various interpretations that they publish. Some religions that you would describe as "bare bones" are intentionally so, and regard the whole "beautiful, living, breathing tapestry of Papal decrees, apocrypha etc" as nothing less than utter heresy and Satanic-influenced defilement of true faith.
If your point is that you personally embrace the "living breathing" thing, fine, but if you're trying to argue that either Christianity or Islam as a whole embrace the idea, I have to disagree, just based on my actual experience with denominations of both that do not.