How exactly does a player come by a grimoire? The rules in the Players Handbook refer to it as an artifact, but it is not listed as one in the GM's guide. Nor is it anywhere in the gear list in the Player's Handbook. It feels like a late addition to make spellcasting slightly less hazardous but not fully fleshed out in the rest of the rules. I haven't read Raven's Purge or the Spire of Quetzel yet, so I'm not sure if any grimoires are mentioned as possible loot in the campaign.
As far as I understand, a player can either find one or make one themselves. The grimoire itself doesn't have any magical properties to it - it's just a collection of written down instructions on how to cast spells. In the equipment section the quill and ink
as well as the parchment
says they can be used to write down spells. Since writing down spells is really good and useful, I would like to think that it consumes one set of quill and ink as well as maybe one sheet of parchment per spell rank or something like that? Obviously that's up to the GM to decide, but I do want there to be some cost to writing down spells.
I do feel like am "empty leather-bound book" or something like that is missing from the equipment list. Just make one up - 6 copper per page, some copper for the leather binding and then a few silver for the work. So maybe 5-20 silver depending on how many pages?