Responsa על פאה 8:11

Also, please instruct us regarding the laws governing the taxation of immovables and books; for I remember what you told us regarding the Mishna, Peah, 8, 9, and the Yerushalmi thereto, that you derived from these sources the rule that immovables be assessed at one quarter their value. Books, I believe, should not be taxed at all; if those who study the books are exempt from taxation, the books themselves ought to be similarly exempt. The Torah is termed "freedom" and ought to be free from the yoke of government. Moreover, house utensils are not taxed. Sometimes a person has many sets of such utensils, which are used only on rare occasions, yet he pays no taxes thereon. How much more reason to exempt books that are used daily by a person or by his sons and sons-in-law, or are lent to others for the purpose of study.