I have played KA for 1 year 2 months and for 9 months with three avatars I have sat on 9 month after month after month while others in my guild have been lucky enough to find 10. Two days ago I sat with one on 8 and the other 2 on 9 and yesterday I opened a box every hour with all 3 avatars a total of 54 boxes and was about to just stop wasting any more time when it happened spell book number 10 I never thought I would see the day. One other person has also found spell book 10. I never gem just use gold every time. I will say as others have posted I know people who have spent vast amounts and still never completed this type of quest. I only post this to show the odds are virtually impossible.
Would show you the screen shots as proof but no idea how you post a screen shot on this forum, if anyone could explain how to do this would be grateful.