I've been seriously involved with photography for only two years but had a bit of an epiphany while spotting a print this weekend (I find spotting meditative). The books that have improved my photography most have been from the "art" section of the bookstore, not the photography section.
[1] It appears that when technique is finally internalized a sense of clarity takes hold, and it becomes clear that the philosophy of photography really can be distilled into the pursuit of vision seeing something more than what is immediately apparent. Can a piece of 18th century French neoclassical architecture become more than an inanimate structure? Can it come alive and evoke an emotion from the viewer?
That is the great intellectual challenge.
I think many of us, myself included, lose this perspective from time to time. We can experiment with film stock, developers, agitation intervals, etc. all we want; these things only serve to realize our thoughts on paper so they may be shared with others. Aren't these creative ideas why we are all driven to make photographs in the first place?
[1] Exception: "Way Beyond Monochrome" by Ralph Lambrecht and Chris Woodhouse