"Liar" and unreliable narrators

I read Liar by Justine Larbalestier just recently. It's a book I'd been looking forward to, because I like unreliable narrators and books that play with reader expectations. But I ended up not really liking it, and I wanted to talk about that, from a narrative perspective.

The following is going to contain huge spoilers for Liar, plus spoilers for Code Name Verity and the first of Karin Lowachee's Warchild novels. I'll cover up those latter spoilers with span text, so you can skip them if you want to remain unspoiled for those books.

( Cut for spoilers )

Has anyone else read it? What did you think? Do you have a different take on the book's reality-to-unreality ratio than I did?