Why the Bible?

Why did God give us the Bible?  I don't mean, Why did God give us His Word.  I mean, Why did God give us His Word in the form in which we have it—66 "books" in their various genres, and forms within those genres: histories, gospels, epistles, apocalyptic, prophetic, poetic, etc.?  Why did He not instead give us an anthology of systematic theology, with a theological dictionary and lexicon in the Appendix?  To be a bit more specific, is the Bible simply a repository of truth, from which we draw for doctrinal formulations and Christian living?  Or is there something about the way in which God has chosen to "put it together", so to speak, that is itself authoritative, and without which it is less authoritative?  That is, to what extent does Scripture lose its authoritative nature as the degree to which we our presentation of it (whether it be preaching, singing, writing, etc.) diverges from its Scriptural form?