There are writers who write novels, and there are writers who write textbooks. While the end results look a lot alike. Both have covers, both have words, both convey concepts, the purpose of the books is completely different. As such, the methodology for writing the book is different. There might even be some commonalities between the two. You might do fact checking between the two... but the facts matter a lot more in a textbook, then a novel. While you actually can use the same process a group of professors use to develop a textbook to write your novel, it doesn't make sense to use the same process a novel writer might use to develop a textbook. To do so would be potentially irresponsible to the students who consume the textbook.