Dynamics in Document Design by Karen Schriver
Dynamics in Document Design is a thick & useful book on how to write clearly & technically. It is a nice companion to legal writing texts. Schriver focuses the writer on being unfalteringly clear in how they communicate to the ‘user’ of their writing.
Think of the audience — think what the questions they are coming to the text with — and think how to answer those questions as clearly & directly as you can.
Schriver’s text is a great handbook for how to achieve usable communication.