Magical scrolls & spell tomes : An Overview

So I read u/CreamWafers' recent post about scrolls and spell tomes, and thought I'd type a quick answer. But this is one of the lore questions that always interested me, and I ended up writing a way longer text than expected. So I decided to make it its own post, and now here it is !
(Disclaimer : this post is not as well-organized as I originally wanted it to be.)

SPELL SCROLLS

The basic principle of a spell scroll is the following : you have to inscribe a magical effect into the paper / parchment you wish to use.
Several points :

— To be effective, the inscription must bear the magic. This can be realized by writing with a special ink, such as tibrol oil. (The ink can be : normal ink which has been later enchanted, an ink bearing alchemical properties, or even of more esoteric origin.)
— Instead, you can write with mundane ink, and pouring magic in the scroll with a petty soul gem or your own magicka, like with a classical enchantment. But you have to enchant the paper / parchment first, the ink will « contain » it.
— The inscriptions need to be mostly written in mage script and / or daedric letters, as both are required to concisely express some notations and concepts.

— In order to cast a scroll's spell, there should be very few requirements. That's why, once folded, the scroll must be engraved with a special seal that you just need to break in order to cast the spell. The seal usually consists of a few common words (enchanted with magic or special ink, cf. supra) that, once read out loud, will activate the spell. These words can be anything you want, really. You can ask your regular enchanter or magescribe to form the seal with an easy-to-remember sentence, such as your favorite line of the Poetic Edda or The Lusty Argonian Maid.
— Safer versions of this are made with the words written in daedric letters ; if you're not overly familiar with it, you'll be less likely to read it by accident.
— Less safe versions are made with a simple enchanted wax seal that you just have to break in order to cast the spell. Risky, yeah, but usable even by illiterate commoners or adventurers !
— Precision : with a bit of experience, artisans can enchant the wax-or-word seal in the same movement as the rest of the scroll, thus sparing some useful resources. (Actually, if this mechanic was implemented in-game with its dedicated skill, that could even be a perk.)

— Scrolls are usually enchanted by professional enchanters (members of a magic organization such as the Mage Guild, or not) and specialized scribes (I can think of some scribes at Gwylim University, or in the Imperial administrations, or independant workers).

SPELL TOMES

Now on spell tomes ! It's quite simple, really.
First, I'll discard the "insta-consuming tome" as an irrelevant gameplay mechanic.

In my view, a spell tome contains several parts of useful information. (Depending on how much, they can have a small to huge number of pages. Some Invocation rituals' manuals can go up to a thousand.)
They usually contain :

— Some preliminary information and warnings, the credits of the scribe and the magic organization he/she belongs to (if relevant). Also, the legality of use of the spell (e.g. "The use of [this spell] is forbidden in the region of [Region] when cast at Men and Mer adult and children and/or in a way susceptible of damaging third party legitimate property").
— An insight on the school of magic the spell belongs to and its general principles (more or less detailed, depending on the level of mastery required for the spell).
— A complete description of the spell : school, effect, element, area, duration, dispelling, magnitude, etc.
— A detailed guide giving precise information on how to cast the spell : gestures, incantations, ritual, needed ingredients (if a ritual, e.g. permanent invocation), method of channeling magic, etc.
— Of course, some safety instructions and things to be wary of when casting the spell.

— Sometimes, finer books are enchanted (or written with special ink) with an effect of Fortify [Intelligence / Willpower / Skill in the concerned magic school] in order to make the learning process easier.

— The reason of the relatively expensive price of spell tomes is that they can't be fully printed. Indeed, they always contain some parts written in mage script or daedric letters, and the printers often have a strong reluctance to print such magical characters. They're already dangerous enough when handwritten, and printers don't want to see an impression error blow up their shop. So these parts are handwritten by scribes on each tome after impression.
— Even when this partly-superstitious reluctance is not present, the printing techniques are not perfect, and mistakes in a spell formula would mean teaching potentially disastrous spells to numerous students.
— Finally, enchanted tomes (cf. supra) are very difficult to print, as the usual enchanted inks' properties don't make them very suitable for use in a printing press. If you want to enchant the book itself instead of the ink, you have to do it before printing, and that means enchanting every page, before printing and assembling. It is a certain loss of time and resources. (And even then, the paper behaves a bit differently when enchanted, so the ink wouldn't permeate it so well.)

Well, that's it, I guess. Do not hesitate to ask for precisions or point out inconsistencies (and/or bad English) ! All criticizing is welcome.