1st thing, right off the bat.....I don't play Savage Worlds so I cannot look at Winter Eternal from the viewpoint of suitability for that game. Instead, I'm looking at it from the perspective of tweaking it as a setting for use in a different RPG game.
The $8 download is 122 pages, secured PDF locked down in the typical manner, which doesn't matter too much for what I think would be normal use of this sourcebook. About the only thing you can't do is change the PDF or extract pages. The PDF is generously bookmarked and has a lot of internal links, but barely comes up a bit short in my opinion. I noticed that the TOC was hyperlinked to go to all the pages listed....you can click on the section or page number, but the Table of Contents itself is not listed as a bookmark.
Say you want to go to the "Waywalkers" section from the TOC. Simple click and you are there. Now if you want to go back to the table of contents you could open the bookmark list and.....it isn't there. The best you could go is click on the first entry and flip back a few pages. Kind of clunky, but still so much better than you find in a lot of PDF sourcebooks. The two page index is in the bookmarks and the page numbers, but not the listed entries, are hyperlinked. This might end up being a bit of a boon to those using the PDF on a tablet since you'd be less likely to "fat finger" it, but I'd prefer things to be hyperlinked consistently.
When looking at a source-book like Winter Eternal, especially when you don't play the game system it is written for, you really have to get hooked into the narrative. While I liked the overall "story" this sourcebook was laying out, it felt a little clunky to me. There were the normal typos here and there (they weren't nearly as frequent as mine are and not worth specifically pointing out) and a few things I was confused as to why they were organized that way (like the Organizations....not alphabetical...are they organized by region alphabetically or just how they fit the pages best?), but in reading the sourcebook like it was a story...I had a persistent nagging feeling that things weren't adding up. Some things just didn't feel "right" to me.
So this planet has it's sun pretty much wiped out instantly and in just a few weeks it starts snowing and before you know it....BAM! the normal outside temperature is -50* C (-58*F). Maybe it took a lot longer for the temps to go to a frozen hell and that gave people enough time to congregate and some to form these cities. I'm sure it didn't help that I had problems understanding the scale of the world as given.....it isn't that big at all.
I love the story, don't get me wrong, and the presence of magic-users, clerics, and druid (basically) can do a lot. It might just be me, but the narrative seems to move too quickly and there are a few contradictions that seem to stand out to me. There aren't trees, but there are because in the cities that have warmth and some protection from the elements the effects of the super-blizzards that reach the warm areas "only" drops the temps to -14*F and in the outlying warm-ish areas it gets to about -22*F and the storms "uproot trees". These storms last a week and occur every 4-8 weeks? Even with some magical intervention it seems "off" to me.
I'm sure this might be nitpicky on my end, but as I'm reading through the book it just gnaws away at me and even when I'm trying to look at this sourcebook objectively the GM in me is thinking of how I could tweak this so it makes sense to me and be useful for my game. For me, just some tweaks to the timeline and temps given makes my inner GM look the other way. Early on in the book, page 7 to be exact, there is one line I'm quite enamored with......"A wave of fire hurled towards the planet and it is believed that everything on the dayside was destroyed instantly." Not on my Ehlerrac buddy......nope.....in my mind's eye a hug fricken asteroid slammed into the planet and caused it to become tidally locked to the sun. Everything goes downhill for the poor planet from there. There could be something akin to a Dark Sun campaign on the sunward side and a whole bunch of lands available on the border as well. BAM! My "problem" is solved.
This is the thing, the problem and the blessing of picking up someone else's game world. What I'm sure makes perfect sense to the author might seem a bit off to you, but it doesn't...or shouldn't matter. Even if you were playing Savage Worlds and wanted to use Winter Eternal you probably should try and tweak things to your liking and make it work for you. Take the larger story elements and tweak as needed. Feel free to toss out what you don't want and add in new stuff to make it your own. Too many GMs don't quite get this.