In canon, the diary was a trap: it was blank, but if you wrote in it, it would write back. Invest enough of yourself in it, and Voldemort could use it to steal your body. Also, it gave Arthur Weasley his best line in all seven books:
Haven’t I told you kids before? Never trust something that can think if you can’t see where it keeps its brain.
...which is relevant enough to MoR’s themes that I’ve been waiting for a subversion to turn up, but no joy so far.
In canon, the diary was a trap: it was blank, but if you wrote in it, it would write back. Invest enough of yourself in it, and Voldemort could use it to steal your body. Also, it gave Arthur Weasley his best line in all seven books:
...which is relevant enough to MoR’s themes that I’ve been waiting for a subversion to turn up, but no joy so far.
As Voldemorte’s horcrux it did that, but I was under the impression that it was originally an actual diary that Riddle wrote in.