I think this is Casey McQuiston's best-executed book yet. I love all of their work, and while this book isn't my favorite book of theirs, I do believe it is by far the best-written. Theo and Kit really feel like robust characters and them being a bit older than McQuiston's other protagonists really aids in them having more fleshed out personalities. Also, the side characters in this book really get to have their own personalities and help drive the plot; they aren't just there to be there. 
This is Casey McQuiston's horniest book yet, it's great, and a hook-up competition is central to the plot, so it makes sense. Highly recommend. 
My gripes with this book are entirely personal in the fact that I don't like Theo and Kit very much as people, so it's a bit harder to root for them as characters. Also, a significant pet peeve of mine is when a foreign language is used in the text and is not translated. I understand that context clues can aid in understanding, but this book had French, Spanish, and Italian. It is a little wild to me to just hope the reader understands. It did not hinder my reading experience but I am someone who can speak/read fairly well in these languages. I know that this is a weird hill to die on.