"This Is Not A Drill" by K. A. Holt

Of course it's not. It's a hammer.

No, I'm kidding. The book is about a lockdown (not the Coronavirus lockdowns, don't worry) at a middle school, because there's an intruder in the building. Nobody thinks it's real at first, but it is. Hence this not being a drill.

This is told entirely in texts (well, and phone notifications, and app comments). And the main character's phone is constantly dying, so various characters keep freaking out because texting is apparently their only form of communication. (One wonders why they don't use their phones as telephones and not high-tech telegraphs.)

It's a fairly tense book. However, I |do wish they'd played the ending straight [ENDING SPOILERS] and had the intruder actually be malicious instead of just some teacher's well-meaning-but-kind-of-dumb ex-husband. It ruined the mood.|

There are a couple of running gags that help alleviate the tension. One of them is a developing news story about escaped therapy llamas, which never actually interact with the story in any meaningful way but show up whenever you run into a "phone notifications" page. The other one, which was funnier to me, is people describing things as "that's like the second rule of lockdown". Which amused me.

(Actually, there's a lot of running gags in this.)

Were this a videogame, I'd rate it: E10+. I think it would be funniest if you made it an old-school-style text adventure, but with a phone-shaped interface so your text adventure had texting.

4 stars, as well.

(Endnote: Every time I encounter something that says "this is not a drill", my mind immediately prompts me to joke about it being some other kind of tool.)