A few things have stood out to me here...
Firstly, buzz and Lost, WELL SAID!!!
Secondly, ignoring "everyone else does it", frankly I don't see anything wrong with Harry Potter as a text itself. Its a journey, its imaginative, there's a lot to talk about.
But I do think other people doing it is an issue, though not as huge as some people seem to think. Mainly because of quotes and etc, what you choose to include. A definate advatage though, is you need nothing about the plot, so you don't need to waste time thinking about how to cram it into half a sentence.
As a few other people have said, DO WHAT YOU KNOW. Seriously, you will write so much better for it. My example, in the half yerarlies for ext 1 crime fiction, was trying to find a supp text, and running out of time, and finally thinking 'stuff it, I'll do Magic Steps'. Magic Steps is a fantasy book about murder, not a crime fiction book. Its also one of my favourite books. I wasn't sure how well it would work, but, with very little preparation on it, that was the text I wrote best about, because I knew it. It was something I'd read previously and enjoyed, and knew a lot about, and it just came so easily. So yeah, write about SOMETHING YOU KNOW.