I just got around to finishing reading it, but I have to say - ever since I 'opened the thing up', I was hooked and wanted to read more.
Prepare for a bit of a glowing review.
I wanted to make sure to update this thread for those of you that might want to read this to see if you should get this or not, or other digital editions, if this is any indicator of the rest of their quality. So if you are one of those people that are reading this thread out of curiosity, this is for you!
I will make clear, first, that I was initially off-put by the release of the Space Marine Centurions as being the sort of 'big next thing' for them. Even the
GW employee at the store said they looked goofy, but then immediately went on to explain how great they were in glowing fashion, and he wasn't even talking about the lore. So I was also very much NOT a fan of them at first, but this is also because I saw them as being something that would be fielded very often, when I thought that given their looks and BACKGROUND...that they should scarcely ever get fielded at all, at least within the lore (as it turns out - I was right; they aren't so frequently seen on battlefields in the lore

).
So yes, disclaimer: If you don't care 2 licks about
40k lore (how are you a
40k fan?) then read no more. If you do, read on.
I bought this $5 digital edition because I was afraid of the Centurions not being WARRANTED to be included in
40k lore, even in the Space Marine armories. I was afraid they simply didn't fit, and were basically just crammed in there without good cause. I have never bought another digital edition anything from
GW before, so this was a first for me.
Apparently, this was simply because I had only read their page in the new Space Marine codex (which I do not own), the lexicanum, and the Warhammer
40k wikia - all of which basically only presented the same amount of very little information about them.
It is because of this that I believe that this digital edition offers 20+ pages of 100% unique content in the form of explanations of the suits history (Age of Apostasy vs Age of Redemption), the construction and discovery of the design, some of the whispers and mutterings of those who constructed it, the rigors the pilot must go through to learn how to use it, histories of engagements, and even a short story involving them. That may not be a complete list, mind you.
In any case, for the purposes of learning about them, and warranting their inclusion into the Space Marines or even the
40k universe at all was PERFECTLY satisfied by this digital edition, and so I have to very, very heartily recommend it to anyone looking for what I was. Case in point, I don't even play Space Marines AND resented these things when I first saw them, and now after reading this even *I* want to buy a squad just to do some converting! I still think that their shoulders could use some tweaks on their models, as well as some of their poses - but looking at that plastic sprue of theirs, how can you *not* see how insanely customizable they are?
Just so you guys know what to expect, this digital edition has only the 1 piece of art for them seen in the
SM codex (besides some always amusing little things of small semi-men doing things like maintenance on bolters by plugging themselves into them), and the only miniatures it displays exist on one page (about page 25) and only show the ones visible on the website anyway, and after that is just legal stuff, etc. So only expect about 21-24 pages of real content, and no rules of any kind.
But for me, that was perfect. I am seriously, very much in love with Centurions now, and if you buy it you'll see why. I could spoil the best stuff within the space of less than a paragraph, but I don't want to

As a hint for one thing, however, I'll say that the unique Centurion honor symbol on their shoulder is very much more meaningful than any of us had thought, before, without having read this digital edition. Suffice it to say this was an extremely enjoyable read.
I will leave you all with this - Centurions are not just big, pointless things that serve no purpose other than to make Terminators look sad. After reading this you understand just how Centurions and Terminators work together. You understand how Centurions are not "easy street" for Astartes, and you understand just how seriously hardcore and awesome they REALLY are. There is no shortage of greatness to be had with them, and customization is very much warranted between different chapters.
Believe it or not, Centurions are absolutely deserving of their space within
40k, 110%.
Oh - and I'll definitely be getting more digital editions in the future now, as well, because of this.