I'll add The Syntopicon as a really good book that Adler wrote (kinda).

1. It's 2 volumes, so not just one book

2. He wrote it with the help of 11 others

3. It's more of a reference manual than a book

4. It's keyed to 58 other books

All the same, The Syntopicon, I feel, is up there with the first Dictionary or Encyclopedia. A titanic effort that helps synthesize the world into a manageable tome.

Getting and being able to use a copy is honestly difficult.

But, dear Reader, worth it at any price. The depth and breadth is amazing and the way he links his 'great ideas' makes traversing the entire history of western thought easy, especially with modern tools.

It's obviously Adler's magnum opus and it shows.

If you'd like to grab a copy, let me know.