Illuminae, by Amie Kaufmann & Jay Kristoff

This brilliant novel had me hooked from its first pages - in which a school is attacked by a huge spaceship. In the heart of the maelstrom are Katy and Ezra, a couple of teenagers who just broke up. We follow their desperate efforts to survive...
From its thrilling opening, Illuminae  builds and builds, with twist after shocking twist. The teenagers are smart and funny and brave, so we're totally with them every step, and share every agony they go through. And there's a lot of that - more than once I muttered, "No!" as I was reading. It's hard not to say more without spoiling the delights.
As well as the exceptional plotting and characterisation, it's an epistolary novel, made up from a stash of emails, analysis of CCTV and other recordings. That's done really well and sustained throughout - no mean achievement in itself - which adds to the intimacy and realism as we look over Katy and Ezra's shoulders.
There are two further books in the same series - Gemina and Obsidio - and the authors are working on a new series, beginning with Aurora Rising next year. They are all added to the reading pile. Illuminae is hugely recommended.