I'd add Pete Dye's Bury Me in a Pot Bunker to any reading list. Shackleford's The Captain is a nice take on Thomas, it has some stuff you won't get in his GCA in America. I personally think anyone who wishes to learn about GCA ought to read Golfing in the Kingdom (Michael Murphy).
Anatomy of a Golf Course, however, is the book, IMHO. It's all encompassing and does not, contrary to what someone said earlier, serve to promote Doak's courses. This notion just kills me. It speaks for what a little success does for a guy, or doesn't do for a guy.
Those who are "in the know" know Doak feels the same way about GCA today as he did 10-15 years ago. For the same reasons today as back then, good is still good, bad is still bad. The only difference is now he's displayed/practiced what he's always preached. Hard to argue with the results.
Any library is incomplete without Tillinghast's book, although I found it sort of dull compared to Hunter and Mackenzie. Nobody has mentioned Klein's book on Ross, or Ross' own book, Golf Has Never Failed Me.
Lastly, as far as what hasn't been mentioned yet, Hurdzan's book is worth looking at at least once, IMHO.