why cant my song book go past 99??

Because that is the limit (although I thought it was 100)..... but either way you can now start "Book2" and continue.  Some folks have a few sorted by genre with titles to reflect the contents.  Originally it was to conserve server space, and thoughtful of that, I keep all my music on my local drive (and backed up) so the tunes are available to me even when there is no internet connection.