So I finally designed the bookcases for my house: standalone cases not built-in shelves, but they're to be screwed into the studs with L-brackets. They're tall (70"), two are 3' wide and two are 4' wide, oak, most shelves 3/4" thick (officially 1", actually 3/4"). 7 shelves for each counting the very top shelf. An upright board on each side to hold the shelves, 3/4" thick and 11 1/2" deep. No back.
Thing is, I went to buy the wood today, and couldn't help thinking as I loaded the wood: OMG, this is heavy. I'll brace them well on the studs, but... I hate to think of this shelf falling on someone, especially a child. I usually try to prevent disaster by making it impossible: say, unplugging the iron to prevent fire rather than trusting the off switch; that kind of thing.
Beginners like me often make things over-sturdy. An expert might be able to make things lighter. But I can't think what else to do to make these light. 1/2" thick shelves would be too flimsy. There's already no back. The upper shelves are less deep than 11 1/2", as they can be, since they're for smaller books.
If you know woodworking... is this pretty much what you would do? Am I missing a way to make things lighter? Or am I just being too paranoid?
I don't think racking is going to be a problem. I've got facing planned at top and bottom which should take care of that. I'm just concerned about making them safe for little ones to be around, and I know I'm an amateur.
If you screw (not nail) it into the studs it won't go anywhere. The floor is holding the weight. As long as you keep it on a short lease (little to no slack), it won't be able to tip very far, meaning there won't be any weight on the screws.
Such an attachment should be of location about the apex of said shelving.
In addition, the opines of http://www.woodbin.com/calcs/sagulator/ would exist in a manner not without sagacity.
A lot more stable with a back. Good luck!