Hey, thanks for your comments. I do agree that the design part is really not present much. And it is hard to get a good book on the subject. I see a few things here
1. Many langs were designed and released by a non-academic settings (Go, Rust many actually, AFAIK). And in non academic settings, I guess it is harder to have a systematic distillation of acquired knowledge over the years. They do not often write papers and things which includes their findings.
2. Because of this reason, many parts of the knowledge you gain by creating a lang, used by several hundred thousand people are often not available easily and hence hard for some fellow researchers to gather and work on it.
3. I also do not know how well defined this field is. With the lack of literature here, if one set out to write a book, a good book nonetheless, how will the person structure this book? What topics will he/she need to discuss? To what extent? ... Do we know the answers to those questions?