I already have read the book "The Martian by Andy Weir" it has lot of "Mark you ruined your life. Again" moments. But to my surprise the Movie doesn’t have those moments.
As a movie it is excellent. It has a new story line, great visuals, superb acting.
Key differences between the book and movie are:
1.(in book)Watney ruins the communication device and looses communication to NASA.
(in Movie)He has constant communication with NASA.
2.(in book)Solar Pannels and other equipment doest fit on the rover in the first attempt. solar pannels stack up high making the rover highly unstable.
(in Movie)for everything there is enough space.
3.(in book)There is a storm on the way to Aries4 mission site. His rover will tip to the site at one point.
(in Movie)nothing happens in the journey.