(This review was originally posted at My Library in the Making.)When I started reading What We Saw At Night, I expected something depressing because the main characters are three diseased teens, but this one caught me completely off-guard. Clearly I should stop skimming through blurbs.Allie Kim and her best friends, Rob and Juliet, have been living with XP (Xeroderma Pigmentosum) their whole lives. To make do with their condition, they are awake at night, experiencing the world in the dark. Juliet introduces Allie and Rob to Parkour, and, though both are reasonably reluctant at first, they decide to join her. One night while tracing, they chance upon a man with a seemingly dead girl in his hands, and the secrets begin unraveling themselves.I love/hate Allie. She was smart and brave - if she wasn't, she wouldn't be doing Parkour - but I thought she was too dependent on her friends. She couldn't bear to stay away from them, even if her pride - and me, internally - was practically screaming at her to do so. Also, at some point, I did wish for Juliet to disappear. She was too angst-y, withdrawn, and complicated for me to love, but I've since realized that I actually love "walking mystery" characters like her (i.e. Alaska from Looking for Alaska by John Green).The shocker-filled plot made my eyes widen and just say "WHAT?!" a lot of times. It was heavy with suspense and mystery (particularly on the characters; everyone had me doubting!), and even though I had to read this over the span of a week, the brilliant writing and thrilling pace never failed to suck me right back into the story. That said, the ending disappointed me. It was too much of cliffhanger for my liking, and I felt like I didn't get a proper conclusion for this book's arc. But yes, there will be a sequel!MY FAVORITE PART was the last scene. It was the abrupt ending I'd said I didn't like, yes, but that also revealed Allie's character development.