"Beyond the stuff like style, conventions, and obvious bugs/problems ..." Catching the obvious issues is IMO one of the main benefits of never skipping code reviews. Even trivial changes often have those (at least when I write them) and I've most likely saved many hours of debugging by a reviewer catching stuff like that. But this does require more than simple rubber stamping. I encourage my reviewers to read my code with the assumption that I make errors, basically looking for the bug that's fairly likely to be there.

The other thing I think is easy to do is simply see if you understand the code. If the reviewer struggle to do understand what's going on, chances are that other people will struggle as well. In this case, your lack of knowledge is an asset, the original author is likely to not see how it looks for someone not as well versed with the problem.