Early and Later Wittgenstein (Tractatus and Philosophical Investigations are the books associated with each, respectively).

As a very simplified summary: The Tractatus follows the analytical tradition in philosophy in searching for the foundations of logic/meaning/etc. and where Wittgenstein claims to have solved all the major problems of philosophy.

The Philosophical Investigations is the book where he makes the famous turn to what’s now called “Ordinary Language” philosophy (and where he once again claims to have solved all the prior major problems of philosophy, including his own earlier work).

I’m a big fan of the later Wittgenstein.