it starts you with xbow, and you unlock more via archery, you can't progress very far with quality OR ammo without the bows class though.
(edit: assuming it's the same in 2.0)
you can unlock as many classes as you like, but it takes some time as you have to acquire knowelege points via scrapping books you don't need, and then combine them later in a research desk.
last time around i went ultimate survivor first, and while it was extremely enjoyable, when i finally got bow class i wanted to cry from relief lol.