If you want necromancy early game, the necromancy of thay appears to unfortunately be Astarion's quest item.
Yes, the book can be used by either Gale or Astarion, instead of by our main character, but I’m guessing it’s not essential for either of them to complete their personal quests. We already know there are other magical items Gale can consume, and I hope that there would be a lot more in the way of warning signs if Astarion can’t achieve whatever benefit he gets from the book in another way too (assuming he can get more than the speak with dead spell anyway).
