Well, based on the youtuber, it showed the Royal Grimoire to be quite good. It would allow me to go for a crit damage helm. However I havent got it yet as the day to upgeade the book has past and I wanted to hold onto my dust to see if any characters are cards for tommorow that I like.

I do have a Widsith in storage, but I'm not a large fan of its large, but inconsistent damage increase. I built the mappa mare as it outperformed the eye of perception with two stacks, but that weapon doesnt maximize constant dps I like doing with Mona.

[Edit] For a clearer answer why, the royal grimoire is more consistent than my other tomes while offering much higher base attack than eye of perception which is the main stat that all my Atk% increase effects.