For each language that we offer, we have a standard set of textbooks that our teachers use. Your teacher should address this in your first few lessons, but if not, there is likely a reason (you're not at the point where a book would help much). But always ask! Let your teacher know you want to use textboooks, if you do.
Your teacher will provide the book details, including ISBN number, for the book(s) they recommend. Most of the books we use are fairly inexpensive, $15 or so.