I am looking for a calculus book and found a good deal, but don't know what they mean by single variable. Please help.
"Single variable" means that it just covers calculus of a single variable. Typically, that covers about the first two semesters of a calculus sequence.
A standard college Calculus text covers both single-variable and multivariable calculus. So the single-variable book probably covers about half the material of a standard text.
Whether that meets your needs .... it all depends. If you're looking for a book for a class, ask your professor. If you're looking for it for self-study, it would probably be fine to start with the single-variable book.