I was wondering if the old trope from TV, where the protagonist finds the old magic tome and reads the spell aloud, causing it to be cast, can be adapted for Ars Magica.
It sounds like the magic tome is a Casting Tablet, which would require the reader to be both Gifted and understand Hermetic casting.
If I postulate that a Tytalus mage decided to make a collection of Casting tablets in the form of a book, and then arranges for someone's apprentice to find it, what spells might be written in the book?
Presupposes that it is standard casting, spells that are useful but capable of getting the caster in challenging situations, and can be cast by someone with score 0 on the required Arts.
What 1/2 dozen or so spells would you that the Tytalus put in this grimoire?
You can get some pretty high level spells out of a Casting Tablet, even with a score of 0 in both Arts. The spell goes off as long as the roll is -30 or more, which means that discounting any Stamina and Aura spells of level 30 or less can be included.
Part of what is in it depends on if you want to possibly splat the user or not. A level 20 ReCo (Base 15, T/M/I) teleport 50 paces straight up might be included. It is not intended to use on yourself but someone might not realize that.
Anything which might cause a violation of the Code would be sure to lead to trouble. Granted scrying will normally fail due to lack of penetration but just the attempt can be bad if found out.
Not an answer to your question, but if you wanted to, you could also craft a magical item (probably an Invested Device) in the shape of book/tome, which you invest with effect, and which are activated by reading aloud the text in the book.
It doesn't have to be a casting tablet.
My first reading of the trope was a charged item, though. Read the incantation loud and the effect takes place. Once.
But it does not have to be just charged.
But, of course, if the target audidence is somebody's apprentice, the casting tablet is more efficient.
As to spells, I would go for scrying spells. Prying Eye, Eyes of the Bat, Eyes of the Eagle, Inexorable Search, all sound good, and there are others. Few things are more effective in keeping magi on their toes as a little scrying menace in the covenant.
Curse of Slumber would also be handy for this little menace, and possibly a shapeshifting spell.
The question here is, trouble to whom? And is that a good or a bad thing from the Tytalian point of view?
Shapechange spell would quickly teach an apprentice that you need to wait out a spell's duration.
Of course, thr grimoire could also have a PeVi spell to negate magic on the caster. But good luck turning the pages to reach that spell. (Perhaps I should specify that the casting tablets are copper sheets, that don't get torn by scrabbling animal claws/talons, etc)
Veil of Invisibility PeIm20 could be similarly interesting. How many apprentices would be tempted to go about unseen, while being fully cognizant of the limitations of the spell (reflections, shadows, dogs smelling you, crowds not avoiding you, etc)
The Core strictly says that you can stipulate a piece of clothing made from the animal, that if removed, negates the spell. But the apprentice will have to get his hands on that, unless the Tytalus was 'kind' enough to provide it...
...So the possessor of the grimoire may need to go on a scavenger hunt to obtain the neccessary props and/or arcane connections for some of the spells.
The other spells that work without props prove that the grimoire works.
I have been thinking why there might be a grimoire of casting tablets where an apprentice might find it.
Perhaps it was originally used in the Gaunrlet of an earlier apprentice. Once the Gauntlet concluded, the grimoire ended up on the back shelf of some Covenant library.
Perhaps the master gave the apprentice a Gauntlet something like - complete the challenge at each of the 6 stations. Successfully complete a challenge and receive a fixed AC to the next station. This grimoire contains all the necessary spells to overcome the challenges, but the fatigue will overcome you. However you will need to cast at least 3 spells from the grimoire in order to succeed. Choose wisely.
If its just the look you are after, I had a bonisagus character with necessary condition: Read spell verbal component from book. He carried around his "spellbook" and when casting, had to open it up and cast from the book.
He had a whole thing about the written word. Sadly that game was killed off by the pandemic.