Ok so I just got my hands on the Imperial Knights Codex. I downloaded the epub version but it’s making me consider getting the hard copy.
Here’s why.
The thing is gorgeous. The artwork is amazing, the heraldry is super cool and even the fluff is really interesting.
I wasn’t very well versed on imperial knights before but I understand em pretty well now, and they are way cooler than I thought.
And that’s the value of this book. It seems the same with the new mini codices. They are more about the fluff and visuals than rules.
As for the rules – nothing different from the white dwarf on model stats so I’m not going there.
They did clarify the rules on stomp attacks a bit so no one can claim entire units are stomped out of play anymore.
The big addition is how the knights come in to your army.
The rumours were true. You can ally them in for a smaller detachment and only a couple surprises in the ally matrix. Tau are desperate allies, while eldar and gk are aoc, the rest of the imperium is bb.
Also an imperial knights ally detachment can be taken in addition to normal allies. So you can bring space marines with eldar allies and an imperial knight ally.
As a primary you get some small rules to basically buff your warlord and make other knights slightly better or worse.
No relics or war gear. Warlord traits there are 2 cool ones in my opinion. One let’s warlord and D3 knights outflank and the other gives IWND to warlord.
So should you buy this book? Well If you just want to play knights you kind of have to but you might wanna get the cheaper epub version.
If you are in to fluff etc hardcopy may be worth it.
Narrating the Forging. 
Glad they clarified the stomp rule, that was just silly. Not sure why some people try to game the system like that.