Oh! I wonder how the Darmesteter translation compares to the one you bought (The Thiselton-Dyer translation)? Let me know how well it reads. I wasn't a fan of Mill's style (waxing poetic King James style) in the Yasna section of the Avesta (the free one online).
The Darmesteter translation is the one I've got. Unfortunately Volume 3 of the Darmesteter's translation (the one that contains the Yasna) is out of print and I don't know if they're planning to print more.
Edit: Actually I've just checked Amazon UK; they're out of the Forgotten Books prints but they have other copies available. Sadly, this book is translated by Lawrence Mills and even on the basic Amazon review there are noticeable mistakes.
And yeah, I think Darmesteter probably waxes KJV-lyrical to the same extent. That's the impression I got from the first few verses of the second Fargard.
Fargard 2 - Yima (Gamshed)
1. Zarathustra asked Ahura Mazda
O Ahura Mazda, most beneficent spirit, Maker of the material world, thou Holy One!
Who was the first mortal before myself, Zarathustra with whom thou, Ahura Mazda, didst convers, whom thou didst teach the law of Ahura, the law of Zarathustra?
2. Ahura Mazda answered:
The fair Yima, the great shepherd O holy Zarathustra! he was the first mortal before thee, Zarathustra, with whom I, Ahura Mazda, did converse, whom I taught the law of Ahura, the law of Zarathustra.