I haven't read the book so can't comment about authenticity. I have seen both movies and enjoyed them for different reasons. I liked Wayne as Cogburn and I suppose having seen that performance first it influenced my appreciation of the character. I think Wayne edged it for his performance which I felt was truer to the craggy, washed-up drunk he was portraying. Having said that I liked Bridges interpretation too but was less convinced. I found the original Maddie extremely annoying and found myself cringing every time she was on screen. I thought Hailee Steinfeld did a much better job and made the character less of a caricature. Glen Campbell for me wasn't believable and I thought Damon did a better job. On the whole I felt the newer version was more authentic in terms of costume and dialogue and I enjoyed the end of the film much more in the sequel.