Tarkovsky's "Stalker" is loosely based on the "Roadside Picnic"[1] a sci-fi novel of Strugatsky brothers.
A. and B. Strugatsky are not that much recognized in the western countries as Andrey Tarkovsky, but they made significant contribution to the Russian literature of XX century, and their books are still popular in the post-soviet countries. In particular, the Roadside Picnic influenced many modern sci-fi works too, including, for example, the "S.T.A.L.K.E.R." and the "Metro" video game series.
Tarkovsky's "Stalker" is quite distinctive from Strugatsky's novel both in style and plot, but the screenplay of the movie was written by Strugatsy brothers too. Basically, they made completely different work in the same setting, but following completely different narrative. Also, they included a lot of pieces from their other (lesser famous) work "The Ugly Swans" into the screenplay, which is closer to Tarkovsky's film style. For example, the Writer's monologue[2] is just a direct translation of the same monologue from The Ugly Swans.
"Solaris", another Tarkovsky's famous sci-fi movie, based on Stanislav Lem's novel of the same title, was a more controversial work. Stanislav Lem made quite critical reception of this adaptation that simplifies and distorted his novel's original ideas. However, I think that Tarkovsky's "Solaris" is still the best adaptation of this book we currently have.
Aside from this, I would recommend "Ivan's Childhood" a war movie about orphaned child, and the "Andrei Rublev" a historical movie about the famous Russian Orthdox icon painter set place in the late middle ages, and about survival of artistic people in hard times.
The reason Stalker is so different from Roadside Picnic is very simply that Tarkovsky made the film twice, the second time without the original script.
He spent an entire summer filming the Strugatskys' original screenplay. But he was using American Kodak 5247 film stock that was found to be out of date. He tried several times to confirm the problem with the Soviet processing lab, but they were unfamiliar with the stock, and only by the time he was done shooting did they realize that the filmed footage was in fact unusable. Tarkovsky himself suspected it may have been sabotage. Apparently (I've never been able to confirm this) the sepia footage at the beginning of the film is from this footage.
Tarkovsky was at this point despondent, not just unhappy with the destruction of his footage, but also with the direction the film was taking, and with his cinematographer (Rerberg, who was critical of the film and the script), whom he fired shortly thereafter. While negotiating with the Soviet film board to get more money and time to reshoot the film, he had several workshops with the Strugatskys to try to develop a better screenplay. Eventually Boris gave up and flew back home, but Arkady persisted, and finally wrote Tarkovsky a short treatment that suggested reducing the entire film to a bare-bones, more philosophical story with nameless characters and very few overt scifi elements. He then encouraged Tarkovsky to go do his own thing.
This appears to have been the breakthrough that helped Tarkovsky find the direction and inspiration he needed, and he used the treatment as the basis for a new screenplay that ended up having very little to do with the book. He wrote enthuastically to Arkady that for the first time as a director he had a screenplay he could call his own. (His previous films had all been written by others, or collaborations, and mostly adaptations.)
Eventually, Tarkovsky was able to negotiate with the film board to shoot a two-part film instead. They would pretend his first shoot, which had already been financed, was the "first part", and he received the necessary funding to shoot the second half. The Strutgatskys, who were still credited, weren't very happy with the final film.
The whole story of Stalker is complicated. I recommend the book "The Films of Andrei Tarkovsky: A Visual Fugue", by Johnson and Petrie, for more information.
A. and B. Strugatsky are not that much recognized in the western countries as Andrey Tarkovsky, but they made significant contribution to the Russian literature of XX century, and their books are still popular in the post-soviet countries. In particular, the Roadside Picnic influenced many modern sci-fi works too, including, for example, the "S.T.A.L.K.E.R." and the "Metro" video game series.
Tarkovsky's "Stalker" is quite distinctive from Strugatsky's novel both in style and plot, but the screenplay of the movie was written by Strugatsy brothers too. Basically, they made completely different work in the same setting, but following completely different narrative. Also, they included a lot of pieces from their other (lesser famous) work "The Ugly Swans" into the screenplay, which is closer to Tarkovsky's film style. For example, the Writer's monologue[2] is just a direct translation of the same monologue from The Ugly Swans.
"Solaris", another Tarkovsky's famous sci-fi movie, based on Stanislav Lem's novel of the same title, was a more controversial work. Stanislav Lem made quite critical reception of this adaptation that simplifies and distorted his novel's original ideas. However, I think that Tarkovsky's "Solaris" is still the best adaptation of this book we currently have.
Aside from this, I would recommend "Ivan's Childhood" a war movie about orphaned child, and the "Andrei Rublev" a historical movie about the famous Russian Orthdox icon painter set place in the late middle ages, and about survival of artistic people in hard times.
[1] https://en.wikipedia.org/wiki/Roadside_Picnic
[2] https://www.youtube.com/watch?v=uwIoSI1Eqak