There are no restrictions in choosing the optional subject for UPSC. So if you are an Arts student, then there are no restrictions for choosing any other subject. As a result, you can obviously choose the Anthropology as an optional subject, but before choosing the subject you must be sure that you can deal with the subject well. If you are interested in the subject then it can be a great experience for you & you preparation.

For the UPSC Anthropology books consider the link below:

https://competition.careers360.com/articles/upsc-anthropology-books

I hope this helps. Wish you a great  day!