As a teacher of English as a Foreign Language I use Michael Swan's book often. It is organized alphabetically by topic and provides clear explanations to various types of usage. Need to find out about the use of the subjunctive form in English or whether it is permitted to use they/them/their to refer to a single indefinite person? This reference can answer those as well as many other elementary or advanced questions that may come up. The only source of confusion I have found was his partial omitting the terms 0,1,2,3 and Mixed Conditional tenses, grouping these all instead under "if". Many students learn the conditional tenses using the 0-M system and find it quite handy and useful in learning the various structures and meanings. The author mentions types 1-3 on pages 245-6, and then goes on to insist quite correctly that there are many different structures for "if". However, he fails to mention the "0" and "M" conditionals, which would account for most of the rest (including conditional sentences that do not use "if"). In all this could be a rather minor irritant to at least some users of this book.

To repeat my view, this is an excellent reference and one I recommend to my advanced students.