It's not for the faint of heart. I refer to Michael Polanyi's 1958 classic Personal Knowledge. It has more about epistemology than most want to know. ["Epistemology" is the study of what can be known and how it is known.]

What I find intriguing is how often Polanyi comes up to the reality of man being in the image of God, looks over the precipice, and then refuses to take the leap. It's a shame. It is a great book and valuable, in spite of its humanistic suppositions. I haven't finished it yet, but have already had my mind stirred.