Personally I’d recommend both. Austin’s is essentially an expansion of his PhD thesis so definitely academic but I found it very accessible. Fridlund has some very interesting stuff on popularity and reception.
I should also point out that the Spaghetti Western at the Crossroads is a collection of papers from different academics. Austin is only the editor of this and contributes one paper I think. This came out of an academic conference held in Luton of all places (Austin used to be based at the University of Bedfordshire) and has pieces written by academics from all over the UK as well as Europe and the U.S. I was at the conference and found it genuinely interesting even though I am not an academic.
