[WARNING: SPOILERS]
While my rating says four stars, I would closer go with a 3.5
First of all, Karen Mc Matthews does an excellent job at keeping the reader engaged. I have read all of the books in the series, and I can confidently say I really enjoyed reading and re-reading them. All the characters were very intriguing and the About That website was a really good plot point. The character arcs, in my opinion, were fine, but I know some people got really attached to them. If you liked this book, you should get the sequels One Of Us is Next and One of Us is Back. In my opinion, they are both better than the original and One Of Us is Next is my favorite book in this trilogy, although I would recommend taking that with a grain of salt as there was a huge time gap between me reading One of Us is Lying and One of Us is Next. In all regards, this is a great YA trilogy for mystery lovers
However, I do have some critiques in regard to the story. For one, I wish the twist of Simon's Suicide was a little more...twist-y? From my perspective, it just seemed like the cast kind of guessed that he killed himself. The moment where Addy confronts Janine would be a much better way for the MCs to come to this conclusion. Also, while I don't have a huge problem with this, it would have been much more effective if one of the main cast DID play a part in Simon's suicide, and were aware of the fact. Unfortunately, this also does not happen in further installments of the series. Another thing, I did not enjoy the romance in this book. I think the main problem with most of the romance (mostly speaking about nate+browyn) is that all the falling-for-each-other kind of just happens offscreen, which greatly reduces the payoff where they finally get together. We don't get to see them interact much before they become a couple. Nate has always liked Browyn, and Browyn just kind of...falls for him. Sure, their midnight calls were cute, but why are they good together? They shouldn't have to outright tell each other why they like each other for us to enjoy them together. Also, Browyn as a character also has some major flaws, one of them being that her personality is just kind of...not there. She's a bit of a Mary Sue, with the only bad thing she's ever done being that she cheated on a test, which like, for high schoolers, is incredibly common. She's smart, beautiful, confident, brave. And Nate just goes from this bad boy drug-dealer to the most amazing man on Planet Earth. Honestly though, Kris and Cooper are the worst perpetrators of this crime. We hardly ever see them interact, Cooper hardly ever explores the fact he's gay, when he and Kris kissed at the end of part one, I was just like "oh okay i guess he's gay now" You can have a couple that gets together offscreeen, but if they're a major plot point, you should probably make them have more development than just '"people who know each other" too "in love". Anyways, sorry for the ramble, not like anyone cares, but man, I could talk about forced romance all day.
For my final review, I would give One of Us is Lying a 3.5/5, but I still do recommend it and the sequels for anyone who wants to read it. And hey, if you enjoy the romance parts, that'll make one of us. Sorry for yapping about that for like five paragraphs.