Whether the players killed a mage and got his spellbook(s) or they met with a nice wizard who let him or her learn a spell from his spellbook, can a player prepare a spell from a spellbook that isn't his or hers?
I'm asking because the PHB p. 114 says:
[…] Preparing a new list of wizard spells requires time spent studying your spellbook and memorizing the incantations and gestures you must make to cast the spell: at least 1 minute per spell level for each spell on your list.
- emphasis mine
Further, the block on the left as a Copying a Spell into the Book ("the" Book as in "your" Book, since it appears in the block titled Your Spellbook), which explains how you can copy a spell from one book to another, assuming the book is from a stranger, it cost more and takes more time. It actually says:
[…] deciphering the unique system of notation used by the system of notation of the wizard who wrote it. […]
It continues saying that you have to learn the various parts of the spell (verbose, material, gesture.)
This makes it sounds like a wizard would have a really hard time to prepare a spell from another's spellbook. Is that the case?
Best Answer
That is correct.
As you quoted, each wizard's spellbook notation is unique, therefore you can't prepare spells from someone else's book.
You must first copy the spell into your own book (deciphering the notation in the process), after which you can prepare it as normal.