Thistle, the protagonist isn't supposed to be a puli, but a pumi, a different breed of shepherd dog, a distinct relative of the border collie and very different from a puli. The novel stresses it right on the first page that he isn't a puli, and there are multiple mentions of the actual breed. Regardless, almost everybody in Hungary thinks Thistle is a puli, and he's always depicted as one, even on illustrations of the original novel.