This book is so meta it's delightful. It's a book about writing and telling stories, mostly, but it also touches on so many different subjects including immortality and knitting. The main character is Meg, a writer who barely making ends meet writing genre fiction under her pen name. Her ambition is to write her "real" novel, the one in which she'll break free from expectations, story structure and genre. In a way, some of what she thinks about really echoed in me. Well, in the first dozen pages I kept exclaiming mentally or out loud that I couldn't believe this book was real because there were just too many coincidences with my life. I'd just finished The Umbrella Academy in which, and this is not a spoiler, a team tries to fend off the end of the world. And on the first page of Our Tragic Universe, Meg is reading a book about surviving the end of the universe. Then of course there's the fact that she's a writer who overthinks her project so much she never actually writes it (touché), and then there are plenty of references including some to Tolkien.
There isn't really a plot here. This book feels more like a conversation with the reader, and I was kind of sorry to read it so fast because I didn't really take time to stop and consider the myriad fascinating writing questions it asked. But I absolutely see myself re-reading it, so it's not really an issue. Writers, this is a book for you! 
Rep: the main character felt like she could be on the ace spectrum but it's never said. One secondary character has OCD. 
CW : a couple of mentions of HP.