Tzitz Eliezer, Part 9, 1:2

(Commenting on Rabbi Meir of Rothenberg’s permission to use money designated for the poor to purchase books for study or to be lent to others.) One can say that he permits this because the books will be lent for study to those who need them, and anyone who needs these books is considered poor, insofar as this person lacks them. This is like distributing spiritual food, and is no less desirable than distributing physical food to those who need it...I have seen an opinion that...one may certainly use this money to buy books for the children of the poor, for providing spiritual food to the poor is also considered to be tzedakah. [translation by Rabbi Jill Jacobs]