Just reading it so far tells us that there's still psionics, there's still space elves, and we still came from a corporate era of technology and expansion.
The differences that can be noted are the Leviathan Gate, the primary means of warping around to places (and likely a less reliable secondary means of warping around or simply extreme-duration cryogenic sublight), and the new name plastered on the space elves. I'm sure we'll see more, but we didn't really have much WH40k canon involved yet in the first place, but now we have no idea what will be waiting for us in the wider universe, what's left of humanity, or what gribblies hide in the dark.
Frankly, I can't wait.