Sometimes a main update is not released at it's usual time, sometimes it comes in either a special time or a surprise time. Expect the unexpected in other words.
Here are some educational guess date candidates for this book to be released,
1.September 3, if this update goes live on this date. This will be a very surprising release.It's the they didn't see that coming moment. It happens sometimes and a great way to start the fall season.
2.October 15, a very special day. Pirate 101 is created. If this is the date,this will be a celebration of a lifetime for active players, a welcome back for returning players. A great welcome for new players. Bring lots of yum for this event.
3.June 21 1st official day of summer. This will make my summer great, if this update goes live on this date.
Here are 3 new educational guess above, until then happy sailing.