Travails with The Alien, a beautifully designed book published by Society for the Preservation of Satyajit Ray Archives, brings out more details about this project. It contains the original short story by Ray, a screenplay for it which was made for a television serial in 1980s, and the complete draft script of The Alien, along with numerous interviews and articles related to the film. There are several photographs and copies of old letters, telegrams and newspaper articles etc. reproduced in the book, and it is a collector's item for Ray enthusiasts.
I felt that the script published in the book is a bit crude with not much of a story to call for. Probably the visual narrative would have made a lot of difference to it if it was made as a movie, or probably there were mode finer details to emerge in the script, as Ray mentions in one of the articles.