We consider a textbook to be a book that:

• Is written for primarily students. Whilst the textbook may also be of interest to other audiences, such as researchers, the main audience should be students
• Supports a course: there must be courses being taught at multiple universities for which the textbook would be suitable. The textbook could either be the only textbook recommended for the course, or it could be a more supplementary textbook that would appear on a recommended reading list. 

Why write a textbook?

There can be several reasons why a textbook gets written:

• There is no textbook on the topic: if this is a relatively new area or perhaps a more niche topic then perhaps no-one has written a textbook to support courses yet
• Existing textbooks are inadequate: perhaps current textbooks don’t cover the topic very well and you have to dip in and out of several different textbooks to cover all the topics you need. Perhaps current textbooks are outdated and haven’t kept up with the research, meaning you have to do a lot of work providing your own notes to supplement these textbooks
• Prestige!: you could write the textbook on the topic and become a household name (in academic circles at least!)
• The opportunity to expand the impact of your educational materials by working with an internationally recognized publisher who can promote and disseminate the textbook  to a global audience