My school's textbook list told me to get a textbook along with a study guide for the course. When I bought the books from someone, the study guide was the same ISBN however, the textbook was different. I looked at the front cover of the study guide and it has the same cover as the textbook.

The textbook's author is the same as well as the title, edition and the publishing year... but the ISBN is different.

When I google the ISBN I got from the school list, nothing comes up except for students trying to sell it on facebook, but when I post up the ISBN that was sold to me, many pages pops up.

Is it the same? Should I keep it or not?