Glad you're liking it, Kelly! It's one of those rare books that I found just browsing in Barnes & Noble when I was in 8th grade... I'd never heard of it before, never read anything by the author, but it sounded interesting, so I got it, and I LOVED it!!! I've read it quite a few times since then, and it's also one of the only young adult books that I read as a kid that I still truly enjoy as an adult. A lot of the other ones I enjoyed at that age seen so cheesy or sappy or over-simplified or formulaic to me now, but I still love this story.
As for the Twilight comparison, I meant mostly in terms of genre. It's not about vampires, obviously, but it has that same blend of romance mixed with suspense and the supernatural aspect. Personally, I also think it's a lot better written, especially the action and suspense parts. Also, I think Ivy is a stronger, more likeable female character, and Tristan, the male lead, is likeable for more than his physical appearance. His physical appearance isn't given much description at all, except we know that he has brown hair and a lean swimmer's body. That's about it. Compared to the pages and pages of Edward description LOL.