What's the goal/deal/rationnel of writing an extremely long textbooks (with exercices?) To be clear, this is not a ranting post. I have never published a book, but recently I have been wondering why are authors writing maths books that is extremely long, say, 600-1600 pages, and the inclusion of exercices makes the question more complicated. Indeed, if a maths book does not have any exercise, then we can somewhat suppose that it serves as a reference book and the book won't play a big role as a textbook. For example nobody complains the lack of exercise on EGA. But in my opinion, if a maths book includes exercises, it automatically qualifies as a textbook. So I wonder, when the book is extremely long, what are the author expecting?…