I found "John, the Maverick Gospel" incredibly illuminating. I read it for a lenten church Bible study class. This is an academic book, but as the subject is the Gospel of John, there certainly is a spiritual/faith dimension to its study. In a way, the book is really dense with lots of material - but it's not a struggle since the ideas and patterns presented are compelling, and provided new insights relating to my own faith journey.
For me, faith certainly is much more than "facts". So looking into the origin and motivation of scripture is not contrary to faith, but enhancing. After all, we are seeking a lens into the lives and struggles of the earliest Christians. That can inform our own lives and struggles in a meaningful way.
The only reason for 4 stars instead of 5 is that I found the whole discussion of post-modernism near the end less than satisfying. However, the breadth of insights in the rest of the book more than made up for this. I really learned a lot.