I did it with my alt in this date and it worked for me so im sure 100% there is not a bug with this quest.
Also please try talk with all npcs again or just relog and talk.
Or maybe you did it once time ago.
I have finish this quest ten minutes ago and nikolai don't give to me the grimoire.
I give all of items to all of the npc, they says to me thank you so i can't make another way to have the grimoire.
But nikolai give to me the ice gladius.
Same problem with buggy blue sage quest, I did it couple of weeks ago.
What I did was:
1) First I talked to Elias, then talked to Peetu, then finish the Investigation part (reward: silk golves from Peetu).
2) Second I talked to Nicolai, to get the List what to do for the Save Books part.
3) Third I talked to Pyry and eradicated the slimes in Library (reward: Ice Gladius from Nicolai).
4) Last I finished the Save Books part, got a thank you but no Grimoire.
Ok, we found the erroneous quest state that prevents this. We are still unable to reproduce the quest state via gameplay. Fix should be coming soon and everyone should be able to receive their missing items.
The secret to getting all the important stuff done is doing nothing.