The galactic civilizations of Foundation vs Three-Body: different takes on scale
The short novel is undervalued as a form. I don't mean the novella — I mean the novel proper that happens to be short: under 200 pages, with the scope and ambition of a novel, just executed with unusual economy. Penelope Fitzgerald is the master of this form. Stoner by John Williams at 278 pages feels like an adequate length. The Stranger by Camus at 128 pages is exactly the right length.
What the short novel requires of its author is complete confidence in every sentence. There's no room for the prose that earns its keep by contributing to atmosphere even when it doesn't advance anything else. Every sentence is under pressure to justify itself.
This is also what the short novel requires of its reader. You can't skim. The economy is the content.