This is a mashup of 4 genres; Steampunk, Western, Mecha, and Planetary Romance
It is an excellent planetary romance with a well developed alien world and ecology, including airships, exotic mounts, and lost technology. The bestiary is one of the best collection of alien beasties you're likely to find anywhere.
It is an excellent alternate-world western with a rich history and varied setting. Many factions and regions are described. Many oneshot adventures and even a plot point campaign are provided.
If they stopped right there 'Old West Planetary Romance' it would be an easy 5 star rating. But then there's a layer of steampunk and mecha slathered on top. Bad science, bad physics, bad economics.... Steampunk and mecha just don't make any sense. Especially when everything else makes so much sense. It just ruins what they've meticulously built by adding this huge dose of unreality.
Sometimes less is more. I can see running 'Westward' as a planetary romance with huge success. But as written I can give it no more than 4 stars. Which is still good, but short of it's potential.
The PDF is bookmarked. Has professional-quality full-colour art throughout. There are a few spelling and grammatical errors as well, but not many.