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?