A better title might have been "Essential Books Mostly from the 20th Century". Which is good and well, but there's thousands of years of great literature to draw from.

And I've read far too little of it.

As for Shakespeare, I prefer Henry IV and King Lear.

Edit: Three books about Theodore Roosevelt? He was Norris-like, but history furnishes a great many awesome badasses. I quite admire Gaius Julius Caesar personally.

I find F. Scott Fitzgerald's The Great Gatsby's placement on the list appropriate and Plato's to be suitably ironic. Gatsby had a library of uncut (i.e. never opened) books and Plato argued against placing too much importance on books themselves versus actually attaining knowledge.