You can easily rig a normal bookcase to do this. You can hinge it like a door to the flat next to it, just make sure that flat is firmly braced. On the oposite end of the bookcase from the hinge add a caster wheel to take some of the weight off the hinge. A little trim can be put along the bottom of the bookcase to hide the wheel.

Dan

We just came out of a play (A Tomb With A View) that needed a secret passageway behind a bookcase. We used four freestanding bookshelves. Three were screwed together. The fourth had casters so that it could be pulled sideways. That took care of the problem of weight distribution and flat reinforcement as would be the case with a swinging bookcase. We had to raise the other bookcases to the same level on the one on casters, and nailed a "kickboard" to hide the gap. A faschia nailed on top of the bookcase extended over the moveable part to make it appear solid and aid in guiding the bookcase as it slid back and forth. The bookcase was equipped on the rear with a broomstick on an eye screw so that it could be moved by an unseen  crew member. It's hard to show such a simple setup without a drawing, but I hope you can imagine it. As the actor entered the set, the bookcase closed "automatically" behind him. Great effect!