+1, I also focus first on readability while reviewing code.

Software engineering is a collaborative process. I don't write code for the machine; I write it for my colleagues and my future self to read. Code we write 6 months ago looks like someone else code. Readability is important unless you're convinced that it's prototype/throwaway code.

After readability then I'd look for tests. It's a theme: good tests are also meant to be read as documentation. Beside ensuring correctness, it's also the example my colleagues or future self can refer for the module usage.