I am familiar with it. My point is why bother using them as skill books. IIRC he can only learn one skill per book. So he'll destroy an entire book of with numerous potion recipes to learn one potion recipe? He'll destroy a book that could be filled with good spells just to learn one spell? Why? The books have excellent guides on how to do the spells, and for all we know even an improperly cast Wingardium Leviosa will let him acquire the spell.
The update stated the following:
[Alert:] You have gained a skillbook for [Charms]. Would you like to use it?
So from this we get the [Charms] skill, not a spell. My guess is that the GM is putting the bulk of basic Charms under one skill, rather than having to deal with each and every Charm as an individual skill since that's a pain in the ass, with those we have access to being determined by a combination of our skill level in Charms, which books we've absorbed, and what Charms we've learned the hard way, with certain noteworthy and advanced spells having their own skills. Either that or the skill provides a blanket boost to all Charms, which is still useful. @Halpo133 can clarify if he wants.
Either way we save time, as creating a skill the hard way involves a time investment.
Y'know, by that logic, I don't see why you're against buying the Arithmancy or Divination books. If they're skillbooks, it'll only take us a moment to learn the skills involved, and we can't really know what those skills will be, exactly. I mean, you're kinda banking that the rune books will be useful, but I'm not sure how/why - enchantment, maybe? - even though according to canon they're basically just a language, so I'm not sure why you're treating the other books any different.
Runes can be a skill we can grind to increase INT without necessarily expending MP during the grinding process. The other two aren't particularly useful, and remember that we only have so much time and money. I cut out the Arithmancy and Divination books because they are stuff I don't really care too much for, as there's more useful skills to spend our finite time grinding.
Divination might be just "vague glimpses into the future", but it could also be things like D&D divination, ie spells for finding specific items/locations/whatever, detecting creatures, remote seeing/listening, things like that. Care of Magical Creatures might have spells or skills for charming monsters in order to make them non-hostile/friendly, or give us knowledge about their traits, abilities and weakpoints.
So, I figure insisting that some of them won't be useful even though we don't know what we might get from them is somewhat couter-productive, to say the least.
Yeah, we might not want to grind every skill we get, but I figure it's better to have the option than not, and any book we don't buy here, we might have trouble getting during the rest of the year.
It's going to be Harry Potter Divination since it's a non-fiction book, which at low levels just reading tea leaves at the bottom of cups and stuff like that.
Keep in mind we can't freely access it due to being a minor - we have to have someone like Hagrid who is authorized to let us make withdrawals.
Frankly, I'd assume all the books are skillbooks. Otherwise, why would the GM have us vote for them?
Not every GM provided option should be assumed to be a useful expenditure of money. GMs have trap options and rather useless options all the time.
Now that I think about it, I'm not to sure if I want to take books from the Hogwarts Library. It's apparent the magical world has security charms that make modern RFID chips and anti-theft systems look like toys. They will know if we took something and apparently destroyed it.
Hell, we'd have to deal with Madame Pince! That lady got pretty possessive around books.
As long as they aren't skillbooks and as long as we check them out through the correct process, we've got no reason not to use the library. Also, IIRC we should be able to read a skillbook the hard way (time consuming, but doable) and get the skill out of it without destroying it, so if we find a skillbook we want in the library we can just spend time reading it.