Brian,
Anything by Geoff, Brad or Tom is a must. I will suggest over time that you acquire Thomas' Golf Architecture in America, probably the best book ever written on the subject. Hunter's Links is a close second along with MacKenzie's Spirit of St Andrews. Simpson's and Wethered's Architectural Side of Golf is also a cornerstone for a serious library. CHeck the Classics of Golf website for some of these titles. They alos carry our own Philip Young's work on Tillinghast which I enjoyed alot. Hre are a few other titles I would suggest.
British Golf Links- Horace Hutchinson
Scotland's Gift- CB Macdonald. I would also get Bahto's book on the man. Very well done.
Golf Courses of the British Isles- Darwin. More of a journey through the great courses in the UK. James Finegan's are also wonderful in their right and his Where courses are great is a fantastic addition.
Missing Links and Lost Links- Daniel Wexler. A must.