Advanced Grammar in Use (2003)

Fourth edition, 2023 Martin Hewings's book picks up where the intermediate Murphy leaves off, for learners at C1 to C2 who already know the rules and now need the finer distinctions. Its 105 units go into the areas that still trip up strong speakers, and the most recent edition added five units on grammar for academic purposes. Those academic units make it the better pick for anyone preparing for study in English or writing reports at work, rather than only polishing conversation. It comes with answers and an eBook, so it works for self-study as well as for a C1 or C2 exam class.