Yeah, I can see most of the book easily converted to movie.

I said they're similar thicknesses because they're right by each other on my bookshelf and are similar thicknesses. I just looked inside for the page counts, and excluding appendices, maps and diagrams of spacecraft, my copy of Project Hail Mary (the original paperback, starting on page 3 and ending on page 476) is just 55 pages shorter than my copy of Dune (50th anniversary paperback, starting on page 1 and ending on 529). Having 10% fewer pages seems pretty reasonable for about as thick. If yours are different by 180 pages, then you've clearly got a different edition of at least one of the books to me with a different font or page size, which is pretty likely given how long Dune's been in print. Given that I didn't even mention page count or word count or the complexity of the prose, just thickness, which could have simply been because of thicker paper, I think your response is unreasonably harsh.

Obviously, I don't disagree that Dune's a more complicated book, but regardless of that, The Martian is much shorter than either, and to turn it into a film, a lot of detail had to go, and a whole act had to be turned into a montage and condensed to Watney modifies a rover and drives to another site, then takes apart a rocket that's waiting for him there. I don't think there's anything simultaneously as large and expendable in Project Hail Mary, yet they obviously need to cut more.

If they cut too many of the flashbacks, it gets rid of, or at least erodes, the WTF? Where am I and how did I get here and why? part of the book, which is a pretty major part of it.