So I've spent hours upon hours making sure I have every single card, but the quest simply wont trigger. The book saids I still have one card left in Velen. But I've checked like 3 times to make sure I have everything. This is really annoying when you're a completionist, because I'm really not willing to start all over if this is a glitch. Anyone else with the same issues, or who knows what I'm talking about? Would be greatly appreciated lads.

this might help:
http://www.gwentcards.com/

have u google for gwent achievement saves? i had problem with lots of achievement as well, i know how fuking frustrating this is. had to revert to save and they worked, havent tried save for gwent yet though. if u dont have save before u collected last card try using someone else save

was actually using that, and multiple other sources