In 1989 I got the book "Thinking on Paper : Refine, Express, and Actually Generate Ideas by Understanding the Processes of the Mind" written by V. A. Howard and M. A. Barton as a gift by my PhD advisor Professor Kristo Ivanov. Kristo gave this book to all PhD students for a while. I assume that he did not appreciate how little we all were writing.
I really liked this book. Today I re-read some parts of it (since I showed it to a colleague yesterday). I found my own notes and comments from 1989 in the book and realized that this book has in many ways shaped my thinking about both writing but maybe even more about design.
The core ideas that the authors present in the book are all highly relevant for design in general and not only for writing. To me, the book presents two core ideas that I still return to. The first is the idea that writing is, what the title says, 'thinking on paper'. The authors explains the difference between writing as articulation and communication. Most writing has to start as articulation and if the writer sees it as communication it becomes a problem. Articulation is the discovery and formulation of ideas, while writing for communication is a process of critique, testing, assessment, and evidence. In relation to this, they also make perfectly clear that writing is not something that happens to you, it is an activity, something you do. There is no "waiting for the Muse".
The other core idea is also visible in the title and that is the idea that to become a better writer you have to understand writing. They write "The first step is to get clear in your mind what writing is, and what it isn't." And the reason for that is because "what you think writing is (or isn't) can profoundly affect how you do it."
To me, this means that the most useful knowledge for design is knowledge about design. This is also a philosophy that I have followed over the years and also why I always stress the importance of theory and philosophy as the most practical ways to improve as a designer. Of course, you also need hands-on skills and knowledge which also the authors take seriously which is why the second part of the book is very hands-on advice based on the notion of 'thinking on paper' on how to structure your writings, how to make an argument, even some about grammar and punctuation.
Anyway, if you are someone who struggles with writing, this is the book for you. If you are a designer, this is a book that presents a highly useful theory about design!