I've read a fair old few and I must say that I think if one were to read The Links, The Spirit of St Andrews, Anatomy of a Golf Course and Geoff Shack's Masters of the Links there's not that much more out there that will enhance your understanding of GCA, plenty for bragging rights at dinner parties, maybe, but not much. I read for pleasure and I enjoy finding voices I enjoy, so I continue... but GCA is not rocket science and once you have a grasp of it (we don't all grasp it the same way) you are unlikely to change your ideals because Tilly tells you to.
Eg - I had never read Behr - still haven't much and so the term 'Line of Charm' was something that I was unaware of before seeing it here, and on Geoff's book. However, once I understood it's meaning, it didn't impart any great new understanding - it's just a cool way of saying what makes sense in strategic design, and play.
Which is not to say that we can't learn new things, find new insights, new angles.. I'll second Rich. Once you've read a few - you are more likely to find new those angles, ideas etc here.