New S.O.S. Assignment Rewards
S.O.S Assignments have said that new assignments are coming soon, for over a year. Since we need more ways to earn Defense Against the Dark Arts Books and Restricted Section Books in order to get the new S.O.S. Skills.
It would make perfect sense to give these books as rewards for the new S.O.S. Assignments. Otherwise, it would take over a year to get the required RSB and over 11.3 years to get the DADA books.