Sharing … Apple Music vs. Apple Books?

We can share our Apple Music subscription with our Family, right, without activating “purchase sharing”. Am I correct that, however, to share Apple Books (at least the ability to READ what we have already purchased) the “organizer” must invoke “purchase sharing”? So, if this is true, then it simply is NOT true that you are allowed to share Apple Books in the same way you share Apple Music. Right?