The Story in Brief
Ryland Grace wakes up alone on a spaceship with no memory of who he is or why he's there. As recollections return in fragments, he pieces together the truth: he's the sole surviving crew member of a last-ditch mission to a distant star, tasked with finding a way to save Earth from an extinction-level threat. The novel's central pleasure is watching a brilliantly curious mind work through impossible problems — and then, unexpectedly, make a friend. Rocky, a five-legged alien engineer Grace meets in deep space, is one of the most inventive alien-contact concepts in recent science fiction. Phil Lord and Christopher Miller, who made The Lego Movie and Spider-Man: Into the Spider-Verse, adapt it with Ryan Gosling as Grace.
Key Differences
Grace's internal monologue
Weir's novel is driven by first-person narration — Grace's voice is funny, self-deprecating, and relentlessly curious, and the slow revelation of his backstory through carefully placed flashbacks creates genuine dread alongside the comedy. The film captures Grace's personality through performance, but Gosling cannot do what the prose does: put you inside a mind that finds genuine delight in each new discovery, no matter how terrifying the situation.
Rocky's communication system
One of the book's great inventions is the musical language Grace and Rocky develop to communicate — Grace works out the physics of Rocky's sound-based speech and they build a shared language from scratch. The novel savours every step of this process. The film necessarily compresses it; the connection between Grace and Rocky arrives faster and with less of the earned difficulty that makes it so moving on the page.
The science
Weir's novel luxuriates in scientific detail — the solutions Grace arrives at are worked out step by methodical step, and the book trusts readers to follow the reasoning. The film compresses the science considerably, which improves pacing but removes the particular pleasure of watching a real problem get solved in real time.
Eva Stratt
In the novel, Stratt is a coldly effective bureaucrat who does whatever it takes to give the mission a chance — she is not likeable, and Weir doesn't ask you to like her. The film warms her considerably. It's a defensible change for a blockbuster, but it softens one of the book's more interesting supporting characters.
Rocky as a practical puppet
This is one area where the film potentially improves on the reading experience. The decision to build Rocky as a practical puppet rather than pure CGI gives the alien an uncanny physical presence that no reader's imagination quite matches. Seeing Rocky move and emote on screen is genuinely affecting in a different way from how it works on the page.
Should You Read First?
Yes — unequivocally. The novel's central pleasure is spending hundreds of pages inside a brilliant, funny, relentlessly curious mind as it unpacks the universe one hypothesis at a time. The film captures the heart of that experience but Weir's prose gives you the full texture of Grace's internal monologue and his almost childlike delight at each new discovery. Read the book, then see the film and watch Gosling do what he can with what the page already established.
Project Hail Mary is one of those rare cases where both versions genuinely earn their existence. The book is the richer, deeper experience — Weir's scientific imagination is best encountered at the page's own pace. The film is a triumph in its own right, and Gosling's Grace is one of the most likeable protagonists in recent blockbuster cinema. Read first. Then go.