Does your program offer a SAS class? At mine, SAS is mandatory; everyone in the epidemiology program graduates with basic knowledge. Check your programs courses to see if it is a requirement or offered as an elective if not. I just don't think a book would be helpful on its own because you really need to use the software to learn how to use it. I don't know much about certificates as my company paid for me to take a class (I learned SAS on the job in college). If your program doesn't offer SAS courses, considering learning python and/or R; they are open source programs so free to download. SAS is too expensive to purchase on your own, but you can see if your school has an agreement with them. If there is no way you can learn SAS as a student, learning another language like R will be helpful for getting jobs that require SAS experience. The consensus is that if you know one language, it's pretty easy to learn another. It was really easy for me to pick up R because of my prior SAS training, even though R is nowhere near as user friendly as SAS. Hope this helps.