[Autumn]

Unless you're a certain kind of Detective, a Book is not the kind of weapon you want to swing at people with. It's weight is less of actual weight (though some cases might say otherwise) and more of how dumb it is to use a book like you would a club.

You could also see a Book's attacks as utilizing spells from the book itself, but that should take much more effort than swinging a sword. Hence, an unwieldy weight.

The Battle Weight part, I figure, could be:
1. Casting takes up your attention quite a bit, leaving your focus on your surroundings and enemies at a sub-par level
2. You like/have to stand still during casting, which doesn't do any favors towards trying to avoid a dagger in your gut
3. You have forsaken exercise so much, it takes more effort to avoid something, and you tend to rely on calculated casts rather than skilled tosses
....and so on and so forth.

OOCly, I see no reason why books shouldn't tell a mage to start lifting. It's part of why dumping STR is not a good idea. (Yes, Fire is tied to STR, but not all mages need Fire ATK to begin with) Considering that spellcasters never have to worry about durability to begin with, I don't think the book weights are unfair.

Relating battle weight to an abstract like that really puts to question as to why STR is the only stat to contribute to B/W, though I see where you are coming from sorta, since you're hauling around a book and not exactly swinging it either most of the time right?

That being said, it would probably solve a lot of problems in the nearby future if base battle weight was just upped a little bit, from 5 base to 10 base because of the aforementioned bug about the weight issues on gloves/shields/shoes/etc.