Jim Hague said:
That's called ad absurdum, what you're doing there.
Yes,
ad absurdum, as in, demonstrating that your argument leads to absurd consequences, which demonstrates a problem with your argument. And it is of course, simply an absurd premise, much less an absurd conclusion, that no one should share their game books.
Libraries are outside the commercial system - the books are checked out, then returned. A library isn't a store - you're comparing apples and oranges to support a shaky point.
I consider taking a library book, copying it on the local copy machine, then sticking it back on the shelf (likely with spine damage after the bout with the copier) as much theft as some jerk pirating off a p2p netowrk; a little worse, in fact, since you've likely damaged the book's spine, reducing its material value.
I'm outside the commercial system too. I lend a book, and it's returned. I'm not a store.
Nobody's suggested lending a book so it can be photocopied (even though if the entire book isn't copied it's legal under fair use, quantity depending on jurisdiction). Don't try to make it seem as though someone has. You have suggested that a group who share a book are somehow immoral. This photocopying line of argument seems to me to be a backpedalling manoeuvre.
There is nothing wrong with sharing your books inside a group. Everyone does it, all the time. If I buy Complete Arcane, I'll let my players use the material within, by reading it out of my copy. To suggest that I demand they buy the book in order to be allowed to use the material is not just unreasonable, it would suggest that I were a few bricks short of a load. Not only should group resource sharing be considered normal for the RPG industry as an axiom for anyone thinking about entering the business, but allow me to remind you once again: Big Bird and Mr. Rogers advocate sharing. Are you trying to tell me that Big Bird is immoral?
Copyright covers right to copy, not right to read. I have the right to allow anyone I like to read any book I own. If you're trying to take that away, you and I have some major differences in opinion over certain fundamental freedoms.