Caveats: I received a review copy of the phone PDF. I used the Books app on an iPhone X to work with the PDF. I'm also going to keep my review here to the format and usability of the phone version of Scion Origin. For my complete thoughts about the game, check out my full episode coverage: https://thestorytold.libsyn.com/episode-16-scion-2nd-edition-origin-overview. The short version is that I love Scion 2nd Edition!
I usually use a mix of physical books and my tablet to access RPG books. I find the physical book usually faster to reference during play, but prefer to sit and read with my tablet. I have occasionally downloaded full PDFs onto my phone for quick reference, but it's often a pain to navigate and deal with the zoom. A dedicated phone version of the PDF works to address readabilty and navigation while maintaining the vision of the original project. Overall, the phone version of Scion Oring succeeds at those requirements.
From a layout perspective, the PDF has a single column of text optomized to be a reasonable size on a phone screen. Looking through the content, I found no need to zoom in and move around on the individual plages, which was the biggest pain using a traditional PDF on my phone. The art appears as either half-page or full page images which don't break up the readability of the text. While it doesn't give complete the effect of the original book, I think it's as good as you could get on a phone and the art does look great.
Navigability and reference is the next area to look at for a phone PDF. This PDF has additional links added to the Table of Contents (ToC) which take you to the relevant sections of the book. From each page, there are additional links that can either take you directly to the ToC or back to whatever page you were on previously. This is especially useful because key terms in the text of the rules are links that take you to the relevant pages. This is especially well done for the antagonists. This makes it very quick to look up most information, especially to get to specific powers your characters has.
What are my gripes about this PDF? I have a few. First, I would have like even more in the ToC. Particulary, I would have like a glossary of rules terms that would take you to the right place in the book. For example, as a player, if I want to look up the specify rules for Enhancements, there's no direct link to get there. There's also no index, which could have potentialy served the same purpose. Additionally, the text linking to key terms is a little inconsistent. Some of the links are bold, but not all bold terms are links and not all links are bold, so it's hard to identify when you have a link and when you don't.
Overall, the question that I would need to ask is would I buy this given that I already have the physical and PDF versions of this book? And that's where I'm not 100% sure yet. To truly answer that, I'm going to have to try using this PDF during a game, which is when I think it's going to be most relevant. I mostly like the navigation and the readability is excellent.