And I just don't understand the Freepers that are coming on the thread and making jokes. As I said, I learned on FR how to use an eye bolt to connect it to the wall so the monstrous TV bookcase couldn't be pulled over. If it hadn't been a serious thread and everyone was making fun of kids dying, no one would have learned any tips.
Another suggestion.
If you have more then one bookcase, attach them together invisibly by screwing them together with screws inserted in unused shelf holes ( if the holes have a sleeve, it can be removed).
Once the units are all attached you can add a couple of angle brackets to attach the entire wall system to wooden wall studs.......Also when installing bookcases on carpet, adjust the front levelers a tad higher the the rear ones....so the case tips back toward the wall. Then, shove the case flat against the wall, having cut out a clearance for baseboards and receptacles.
If you don't have levelers, just shim the fronts with a piece of cedar shingle.