Bloodbook

You attempt to redirect knowledge of a spell to a book from a dead spellcaster. the spellcaster cannot be dead longer than 10 days (effects like gentle repose can extend this period). you place an empty book open on the chest of a dead spellcaster. you lay bone dust in a circle around the book and splash the vile of blood on the book. you place both copper pieces on the eyes of the creature and rub graveyard dirt on the foreheard in an arc shape. you mutter some necromacy trigger words nd the blood on the book glows vibrant. The body cracks and moves and fits the shape around the book. the book is slammed shut magically and those around it can hear scratches on the inside. after 1 minute the sounds stop and the book is new. the book has a bone collar and runes covering the book. inside, is an inscription that only the spell user can read as their blood was binded to this book (spells such as comprehend languages or abilities to read all writing does not penetrate this spell). You have a list of all the spells known to the creature and must pick one that you can use without expending a spell slot. once done so, the book disintegrates into a puddle of the dead spellcasters blood.