I have got the task of sharing my opinion of the new books, and my personal opinion of where the Hobby is going.
They immediately feel very different to the old Codex format. They feel to me as if they are the last 30% of an old 40k Codex. The old pages upon pages of background, colour schemes, mini stories, iconography and source images are gone. Instead this feels as if it is a one page summary of the army and onto the army list.
The art work is rich and beautifully presented, with lots of historic pieces.
The page layouts are very well laid out and easy to jump from list to list.
I loved the old Codex format. I loved how you had the options on top of one another or contained under a unit entry, but with a change to the way lists can be made in the new 8th ed, Matched play (points system) has been made a bit less easy to prepare in my opinion, as I was very used to the old way of "I want a Space Marine Squad so I will go to that page and add up what I want" system.
I am sad that the richness about the army and character (this force is like this because of their dread history and this chapter here hates this enemy) of the lesser known forces such as sub forces of that faction (sons of decay, Lords of pleasure etc), has now just vanished. I don't know if it will appear elsewhere, or if it is just the books I have.
I think these books are just mainly designed to make your forces from 7th edition compatible with 8th as on first glance there are no new options in here. Those will probably be appearing in white Dwarf first and then annually in Chapter approved. Looking at the way the Space Marines have changed so dramatically in the last month, I can now imagine the same with the rest of the 7th ed range.
I personally think digital is the only way to go now to keep on top with the hurricane of changes, but these books are a must to play in 8tg edition and are very easy to enable you play to the new list creation options.