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.