The Long Walk by Slawomir Rawicz (New York: Harper, 1956) was reprinted several times and even digitized. However, as I read it, I began to question the narrative. The writer told of surviving more than a week in the Gobi Desert in the summer without so much as taking a drink of water, and of meeting "abominable snowmen" in the Himalayas. By the time I finished, I was convinced that this was a work of fiction.
I read the book years ago when it was still believed by some, and long before the recent claims by another fellow, supported by his own manuscript from which Rawicz ripped off the story, and like you, I didn’t quite believe it.
But as you can see, there are emotional attachments to lies about history, especially lies that one believed for a long time.