"Where the hills howl" by Francisco Narla is number 1 of the 32 historical novels of all times to read now according to ELLE magazine.
Two things they like most about this historical novel that takes place in Roman times: it has less than 300 pages (a record for the genre) and the real protagonist is, indeed, a wolf.
A group of legionnaires loyal to Julius Caesar pretend to be animal keepers to put an end to the wolves that are destroying the crops of a Galician tribe, while their actual aim is to win them over and be told where some legendary gold mines are.