Pronouns are defined as words that replace nouns in the sentences. Or in other words, pronouns are words that take the place of a noun. In English grammar, there are different types of pronouns such as demonstrative pronoun, Indefinite Pronouns, Interrogative Pronouns, Reflexive Pronouns, Relative Pronouns, Personal Pronouns, and Possessive Pronouns.
In addition, in English grammar, first-person pronouns are the ones which refer to the speaker/writer, second-person pronouns are the one used when a speaker is addressing one or more individuals, and third-person pronouns refer to either people or things other than the speaker/writer and the person or persons addressed.
From all the pronouns which can be identified in the sentence provided, I know you finished reading his book, which is about Jamestown, none correspond to a third-person personal pronoun, since "I" correspond to a first-person personal pronoun, "you" corresponds to a second-person personal pronoun, "which" correspond to a relative pronoun and "his" correspond to a third-person pronoun, however, it is not personal but possessive.
