Two questions involving my WH.

The Mastery Book is a reward for reaching 4th. 3rd was the Scroll. o_O

Oops. When did you reach 4th job then? Let me refer to the notes in the meanwhile.

EDIT: Here's the text about the event:

Those who do their third job advancement will receive a special 70% scroll for their type of weapon, and finally those who do the 4th job advancement during this event will receive a free Special Mastery Book~

That basically means you should get the book since you got the scroll.