If it's one book, it has to be Tom Doak's book.
But it should be many books. In that case, I would start with a book called "The Art of Golf Design". It's full of Michael Miller's paintings and it has some essays by Shackelford that relate to the paintings. But it also contains a number of essays and short remarks by the ODGs, and especially important amongst those are writings by Max Behr.
If you have that book, then sitting close by should be the Big Four 1920s books (Golf Architecture, The Links, GA in America, The Architectural Side of Golf) because the references in the Miller book point one to the full material. Anatomy of a Golf Course would still be essential.
If you've gotten that far, then you're ready to think more about what was and what is. Use Wexler's two Lost Links books. On my shelf they get a lot of wear.
My kids aren't too interested in golf architecture right now, but they may be more so later. I've left instructions on how to care for/dispose of my GA library after I am gone. But in case they want to learn without my help, I took a volume of Miller's book, labeled it "START HERE", and annotated the interior with notes on how to refer to the books in the rest of my library. That volume is a good catch-all for concepts and the paintings will get the layman interested.
And we shouldn't forget the old World Atlas of Golf -- many of us got a start there!