Project Hail Mary is a story by the same author of The Martian, Andy Weir. While The Martian's story is grounded in the science we understand today, Project Hail Mary goes beyond that and adds more sci-fi but does so without breaking the rules of science.
The other difference between The Martian and Project Hail Mary is the scope. In The Martian, Mark Watney is stranded on Mars and needs to figure out how to get home. In Project Hail Mary, the Sun is being destroyed by a phenomenon, and Ryland Grace must travel to a distant star to figure out how to save Earth.
The protagonist, Ryland Grace, is a science teacher who ends up as the sole survivor of the Hail Mary as it travels to its destination, where we hope to figure out how to save Earth. Ryland wakes from a coma with no memory of how he got there or even who he is. Fortunately, his memory comes back over time.
As Ryland is solving one problem after another aboard the Hail Mary, his memories slowly return. We see the planning of the Project Hail Mary mission on Earth and how Ryland was "chosen" for the mission. We also see the sacrifices that are made to make the mission happen.
The writing is engaging and fun. While there is a lot of math involved, you can get the point without understanding it. It all makes sense. This is one of the special things about Andy Weir's writing style. You can tell he loves this stuff. He spent a lot of time researching and discussing "what if" scenarios with real scientists and astronauts. After the success of The Martian, he likely has a pool of resources available to him.
This story is not your typical sci-fi. I felt like this could actually happen. Ryland's problems were science-based and felt realistic, opposed to forced plot twists just to make the story exciting. There were many times in this book where I imagined all of the things that could have been done if this were an action sci-fi story that we would typically see. Instead, we get a great story about a guy working out extraordinary problems.
I really enjoyed this book.
“Working the problem” - NASA
By the way, a Project Hail Mary movie is being made, starring Ryan Gosling.