Well, he sent them to those publishing companies last year.
They have those science divulgation collections and I think they don't get many books on maths, so they were quite interested.
The first one went thru several style editors (it's funny to see how they made completely different suggestions) but left the maths to him, so it was all quite fast. My husband read his own book four or five times in a month
It got published on January.
The other one was slower. The company has an science editor which suggested to change some minor details. Nothing big though.
They planned to publish late this year, but apparently they had a problem with the book they were planning to release earlier in the collection (they detected plagiarism!) and decided to move this one up. So everything was very very fast.
It got published on March.
I had no idea proofreaders ever worked on site.
Editors would make more sense. Or at least the head of the editors.
But if you need to read stuff I would rather do it quietly at home than in a noisy office.