No. If you adopt a Pet that has read, say, 300 unique books, you will not be able to claim any rewards for reading your Pet 300 books. You will, however, be able to claim all subsequent rewards for any milestones you reach after that!
No. If you adopt a Pet that has read, say, 300 unique books, you will not be able to claim any rewards for reading your Pet 300 books. You will, however, be able to claim all subsequent rewards for any milestones you reach after that!