The highest roi I ever found for critical thinking enhancement was LSAT prep. Specifically, the logical reasoning section has you evaluate a series of argument

The highest roi I ever found for critical thinking enhancement was LSAT prep. Specifically, the logical reasoning section has you evaluate a series of arguments and answer (often tricky) questions about the argument--analogizing, finding flaws, etc. Formal books etc are fine, but if this were programming, I'd say dive in and write code. Imo LSAT prep is the 'write code' in this instance.