Quick-take: Worthy successor to The Martian.
Dr. Ryland Grace wakes up with a bad case of amnesia. Through experimentation, and flashbacks, he gradually figures he is on a space ship tasked with saving humanity from an invasive species he has called Astrophage.
I'm stopping my mini-summary there because each little nugget of knowledge is an important reveal. This book can be classified as 80% sci-fi, 10% mystery (as Dr. Grace works through his amnesia and science experiments, more important plot points are found), and the remaining 10% could be called pure fantasy. Astrophage is an amazing species found in pure technobabble that is impossible to believe. However, I am willing to overlook it (with some difficulty because of how outrageously fantastical it is) because there are a lot of things to like with the book.
I was not that impressed with Artemis. My main complaint is that the book was just a reactionary novel with incompetent characters solving their own problem they created, and it just happened to take place on the Moon. There was nothing interesting other than, "Hey, we are on the moon."
With Project Hail Mary, Andy Weir has gone back to what made the Martian enjoyable. There is a real problem. It not anybody's fault, but it needs to be solved, and it will take a lot of creativity, science, and grit to get it done. The main character is up to the task, and we are along for the ride.
The book is loaded with science. I am not skilled in the hard sciences. Dr. Grace seems pretty adept, and I am wondering if Andy Weir had an advisor for portions of it. Dr. Grace is constantly making theories and running tests, and they are explained, and a lot of it sounds... plausible. However, even I at times perk up thinking, "Ok.. that seems like a bit of a stretch." I wish I actually knew which portions of this book are real science and which are just technobabble to help the plot. Andy Weir makes no distinctions.
Score: 5/5. The book is not as good as The Martian. Everything about The Martian felt like it could actually happen. This one just has far too many fantastical elements. However, it was enjoyable. I am pleased their is now a worthy successor. If you are a fan, skip Artemis and pick up this one.