hellywelly...here it is :::
https://en.wikipedia.org/wiki/The_Searchers_(film)
I think we read the book in school because of the massive success of the John Ford film, rather the merits of the book, good though the book is.
If you read the link, you can see that the book was probably based on a real life case in 1836. The Comanches had a habit of taking slaves as captives, and its unlikely that this was an isolated incident.
Great film, as all John Ford's are and a worthwhile book to read.
I can also remember reading the Kon-Tiki book, by Thor Heyerdahl ::
https://en.wikipedia.org/wiki/The_Kon-Tiki_Expedition:_By_Raft_Across_the_South_Seas
Actually, I found a second hand book of the above in our local Co-op, only last week and its on my bedside table, ready to go ( with about 10 others of course, so it will have to wait its turn ! )