The Story in Brief
Botanist and astronaut Mark Watney is accidentally left behind on Mars after a dust storm forces his crew to abort their mission. Presumed dead, with no way to communicate with Earth and not enough food to survive until a rescue is possible, Watney must science his way through survival — growing food in Martian soil, improvising communication, and crossing hundreds of miles of hostile terrain in a rover held together by optimism and duct tape. Andy Weir self-published the novel after serialising it online; it became a phenomenon and made him the template for a new kind of hard science fiction. Ridley Scott directed the film with Matt Damon as Watney.
Key Differences
Watney's log entries
The novel is structured around Watney's written logs — first-person problem-solving narrated by a man who refuses to catastrophize and finds the funny side of dying on Mars. This voice is the book's greatest achievement. The film preserves Watney's humour through performance and some direct-to-camera moments, but Damon can't fully replicate the experience of being inside a mind that is simultaneously terrified and finding everything a bit ridiculous.
The science
Weir's novel is exhaustively researched and the solutions Watney arrives at are worked through in real detail — the potato farming, the water production, the navigation. The book trusts readers to follow the maths. Scott's film compresses the science considerably, which tightens the pacing at the cost of the particular satisfaction Weir offers: watching a real problem get solved correctly.
The Sol-by-Sol structure
The novel tracks Watney's survival day by Martian day — Sol 6, Sol 38, Sol 119 — which gives the reader a genuine sense of the duration of his ordeal and the accumulating weight of isolation. The film compresses this significantly. Several disaster sequences are removed or merged, which improves momentum but removes the grinding, relentless quality that makes Watney's survival feel genuinely earned.
The emotional tone
There is a quiet emotional undertow in the novel — loneliness, the strangeness of being the only human on an entire planet — that the film, in its crowd-pleasing mode, mostly replaces with uplift and ensemble camaraderie. Scott's film is more conventionally heroic. Weir's book is funnier and sadder at the same time.
The rescue sequence
This is one area where the film unambiguously improves on the source. Scott's third-act rescue is a masterpiece of cross-cutting and editing — the visual storytelling of Watney's space walk and the crew's response is more viscerally effective than Weir's prose version of the same events.
Should You Read First?
The book and film are closely matched — either works as an entry point, which is unusual. The book is more technically detailed and funnier; the film is better paced and Damon is definitive Watney. If you've already seen the film, the book will give you everything Scott had to leave out. If you liked Project Hail Mary, read The Martian and see exactly where Weir learned his craft.
A genuinely close call — one of the better-matched book-film pairs in recent memory. The book is funnier and more technically rich; the film is better paced and Scott's rescue sequence is extraordinary. Read both. Start wherever you like.