Can the wizard in our group prepare a spell from the spellbook of an NPC wizard?

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?

Can a multiclass Wizard copy any Wizard spell they find into their spellbook?

The Wizard includes the following feature:

Copying a Spell into the Book. When you find a wizard spell of 1st level or higher, you can add it to your spellbook if it is of a level for which you have spell slots and if you can spare the time to decipher and copy it.

Does this mean that a Wizard 1/Cleric 19 can copy any Wizard spell they find into their spellbook?

Is there anything preventing them from casting these spells?

Can a multi-class Bard/Wizard write spells known from Bard, into Wizard spellbook?

Can a multi-class Bard/Wizard write spells known from their Bard class, into their wizard spellbook?

e.g. they know the Comprehend Languages as a Bard spell, and want to write it directly into their wizard’s spellbook?

And what is the cost? … i.e. 1 hour and 10 gp because they know it, or 2 hours and 50 gp because they have to experiment with casting it as a wizard?

Can I copy prepared Cleric spells that are also on the Wizard spell list into my spellbook?

I’m multiclassing as a Wizard2/Cleric3. I’m wondering if it’s possible to prepare a spell from the cleric spell list and then if it’s also found in the Wizard spell list, would I be able to write it down in my wizard spellbook?

I’m confused by this as the PHB states that if I find a scroll or a book, I can decipher it and boom, it’s in my own book. I’m essentially my own walking book book. I’ve found this in the sidebar in the PHB under wizard regarding spellbooks.

Replacing the Book. You can copy a spell form your own spellbook into another book-for example, if you want too make a backup copy of your spellbook. This is just like copying a new spell into your spellbook, but faster and easier since you understand your own notation and already know how to cast the spell. You spend only 1 hour and 10gp for each level of the copied spell.

If you lose your spellbook, you can use the same procedure to transcribe the spells that you have prepared into a new spellbook. Filling out the remainder of yourspellbook requires you to find new spells to do so, as normal. For this reason, many wizards keep backup spellbooks in a safe place.

Now, lets say that I prepare Protection from Evil and Good, which is a 1st level spell and can both be found in the Cleric spells list and in the Wizard spell list. Shouldn’t it be possible for me to write it down into my spellbook by following the given formula in the “Replacing the Book”; 10gp + 1hour for each level of the copied spell.

I understand that it would have been very different if the holder of the spell I want to copy is another creature (party member or not) but now it’s all me. I know the spells, I own the book, I am the Wizard.

Can a wizard with cleric levels scribe wizard spells he had prepared from the cleric class in his spellbook?

There’s been a debate on a D&D discord server that’s caused me a lot of trouble. Here is the question: if a wizard 2/cleric 2 has a wizard spell prepared from being a cleric, rather than from being a wizard, then should the wizard-cleric not be able to then scribe that spell into their spellbook the same as if they had it prepared from anywhere else?

Edit: This is different to the bard/wizard question due to bards having spells known, and clerics preparing spells just as wizards do.

Is it possible to create a divine spellbook?

The mnemonic vestment says this:

If the wearer is a spontaneous caster, once per day she may use a spell slot to cast a spell from a written source (such as a scroll or spellbook) as if she knew that spell. The spell must be on her spell list, the same spell level or lower than the expended spell slot, and the same type of spell (arcane or divine) as the spell slot expended.

The only classes I can find that use a spellbook are all arcane casters or archetypes that grant arcane casting. Is the spellbook an option that’s only available to arcane casters, or could a divine caster make a spellbook of divine spells even if it can’t be used to actually prepare spells?

Can more than one wizard copy a spell from a spellbook?

In the PLAYER’S HANDBOOK you can copy a spell into your own spellbook. In the DMG (p200) if a spell is copied from a scroll, the scroll is destroyed. If a spell is copied from a spellbook however, does the same apply? And could more than one wizard copy the same spell (or spells) from a found spellbook?

My thoughts are that more than more wizard could copy the same spell from a book. Two key reasons being; scrolls are consumable items (whereas spellbooks are not), and wizards can make a copy (or multiple copies) of their own spellbooks without destroying them.

Can non-wizards decipher a wizard’s spellbook?

In the wizard’s class description, it says that

When you find a wizard spell of 1st level or higher, you can add it to your spellbook if it is of a spell level you can prepare and if you can spare the time to decipher and copy it.

Is the ability to decipher a wizard’s spellbook therefore unique to wizards, or would someone without any wizard levels still be able to decipher a spellbook to read what the spells are?

Could a spellbook be destroyed/emptied by being viewed by someone else?

In my first ever game of D&D (this was many years ago), I joined an existing game, and at the table, I was sitting beside a player playing a wizard (or “Magic User” to use the parlance of the time). The player had a little notebook to represent her spell-book, so at one point out of idle curiosity, I picked it up and flicked through it.

Another player at the table jumped up and pointed, shouting out with glee (we were kids) that I had read the wizard’s spell-book, as it turns out that if anyone other than the wizard herself looks at it, all the spells would vanish from the book.

So the GM declared that this indeed is what happened, she would have to start a new spellbook, collecting her spells all over again and the wizard player spent the rest of the session understandably unhappy, glaring & cursing at me and so on.

Has this ever been a rule in D&D?

In all my years of playing (OD&D – which I believe this was, AD&D 2nd Ed, 3, 3.5, etc.) I have never come across a rule like this. I suppose it’s possible she had a curse or something but in the ensuing argument this was never mentioned – they seemed to be making out that it was just a rule about spellbooks, and that I should have just somehow known not to do this.

Can a Simulacrum of a wizard use the wizard’s spellbook?

Suppose a wizard casts Simulacrum on their self, creating a duplicate who has all the same spells prepared and has all the same spell slots (minus the 7th level slot used to cast Simulacrum, of course). Can the duplicate use the wizard’s spellbook to do any of the following?

  1. Prepare new spells after a long rest
  2. Cast spells as rituals
  3. Copy new spells into the book
  4. Copy their currently prepared spells into a new book that is then usable by the original wizard

Which of those, if any, is the duplicate capable of doing? Is there anything the duplicate can’t do with the spellbook that the original wizard can?