A person can be infallible.
A book can be inerrant.
A book (i.e., the bible) can’t be infallible because it doesn’t teach anything. Only persons teach.
So, while a book may not contain any error, there is nothing it can do (as an inanimate object) to keep you from misinterpreting it.
A person (i.e.the pope) can be infallible in his teaching, with respect to matters of faith and morals (because protected from teaching error by the Holy Spirit.)