For a reference grammar book, Pratical English Usage by Swan is an excellent reference for teachers and for relatively advanced students. https://en.wikipedia.org/wiki/Practical_English_Usage excerpt Practical English Usage is a standard reference book aimed at foreign learners of English and their teachers written by Michael Swan. Published by Oxford University Press, it has sold over 2 million copies since the first edition was published in 1980.[1] A new, and greatly extended second edition was published in 1995. A third edition was released in 2005, and a fourth in 2016.

I've always liked the format of the Cambridge "Grammar in Use" series:it is brief, to-the-point, and practical, with lots of examples. They have editions for beginning, intermediate, and advanced learners. Here's a link to sample sections from the intermediate book: https://www.cambridge.org/us/cambridgeenglish/catalog/grammar-vocabulary-and-pronunciation/english-grammar-use-4th-edition/content/sample-units And here's the same for their advanced book: https://www.cambridge.org/us/cambridgeenglish/catalog/grammar-vocabulary-and-pronunciation/advanced-grammar-use-3rd-edition/content/sample-units

Another vote for Grammar in Use by Murphy. The two-page units consist of a page of explanations and a page of exercises. Some editions have the answers in the back. It has a self-test which allows study to identify problems areas and work on those (instead of the whole book). It is useful while learning and useful later for review. There is an associated workbook with no explanations, just exercises.