A Fistful Of Dollars owed a lot to an earlier Japanese samurai movie.
Not just any Samurai movie! Kurosawa's Yojimbo, of which I would say Fistful basically ripped off. Kurosawa's film Hidden Fortress also heavily influenced Star Wars.
I've been wanting to get into westerns too. Watched plenty film-wise, but never read any. Started McCarthy's No Country for Old Men recently, and I also have Blood Meridian on my shelf, alongside 2 D'Amour books (Hondo - supposedly the greatest Western novel ever, if John Wayne is anyone to go by - and Taggart) . I also have a copy of the novel, True Grit.