Many years ago I worked in the typesetting industry across the UK and much of the rest of the world. At the time I noted that many clients had a well-thumbed copy of a book called Hart’s Rules for Compositors and Readers. This small green book was indispensable and the wiki page is worth a look if you want more history. My advice is that you should consider getting one of these even if you have other style guides.
If you want to know more please carry on – I’ve also identified some relevant links.
Why two Hart’s?
In reality there are many versions of Hart’s Rules and the green one that I have is the 39th edition from 1983 (reprinted in 1984). If you want a brand new book then the only option is the blue version (the one pictured is New Hart’s Rules 2005 adapted from the 2002 Oxford Guide to Style). I have no doubt that the later version is more than fine but that isn’t the point! If you do ever see the green book around I suggest you have a look; if nothing else you should consider the blue.
All this doesn’t stop me from owning the excellent and much referenced Elements of Style by Strunk & White which I also recommend.
Oxford University Press (OUP) advertise the book and also provide some basic guidance: House Style
An affiliate free link to Amazon: New Hart’s Rules
Historians might like to peruse this 1905 version on the Internet Archive: Rules for Compositors and Readers at the University Press, Oxford (1905)