Well, you should be able to find a textbook on Amazon or a similar website at any time of the year, not just when schools are in session. If you don't know the edition of the book, then you may want to try to find that out before you buy an edition since problems can be different in different editions.
Also, I don't know what you mean by "Coates," nor do I know what course 2425 corresponds to. Course numbers vary from institution to institution, and, while it may not help us find your correct edition, it is useful to use course names, instead of numbers here. It makes things much clearer for people who do not go to your school but want to try to help you out.