I've loved the books so far in the series with a captial L. This one? I just can't get into it. I think part of it is that everyone just seems so ridiculously mean to the main characters that it's just a little bit unbelievable. I know that people can get callous & cruel, but some of the plotlines seem a little too farfetched. The best example is Kate (spoiler) who tricks Aria into spilling that she has an STD (which may or may not be true), making Kate run & tattle to Aria's parents, which makes the parents make Aria spend all her waking time with Kate. That's just too farfetched even for a soap opera. (Ok, I skipped ahead in the book some.) That's just too overly complicated.
I'm going to try giving it another chance b/c I loved the previous books so much, but I just can't work up the enthusiasm like I can. It's not the whole Mona thing either- I can totally see where there would be another A & that there's still Ali's killer at large (if she was even dead). I don't know what it is, I just can't get into this book.