We did wind up watching Project Hail Mary over the weekend. Overall I liked it. If you enjoyed films like The Martian and Arrival, you'll probably like this one, as I thought PHM could be thought of as sort of a mashup of the two. Maybe some similarities to Interstellar as well, though, imo, not as much as the other two.
It felt a little draggy at times, so I thought maybe it could've been shortened up a little bit. Though I'm not sure what could've been cut out, so maybe it didn't need to be shorter, just maybe find a way to spice up a couple of points where it got too slow.
But those are minor criticisms. On the whole I enjoyed it and am not sorry I spent money to see it.
Apparently the book goes into more technical (and accurate, I hear) space travel stuff. Like how time slows down the faster you go. This wasn't explicitly mentioned in the film, but there was a nod to it at the end when you see the woman who sent Ryan Gosling to space, and she's markedly older. There's no explanation for that in the movie, but I assume that was further described in the book, how a more limited amount of time had passed for Gosling traveling through space, while more time had passed on Earth.
Anyway, I give it a thumbs up.