I have it, and while the theory looks stocksolid, it does require you to have a ton of prior knowledge about the Spanish and probably even the Archangel.
It's not a complete repertoire (so you'll need to find a solution vs Exchange etc from elsewhere), and there is very little if anything about "general considerations".
Mostly just moves, and mostly cutting out where he sees equality - which I'm sure is correct, but if you aren't sure how to continue playing, that doesn't help too much.
Certainly ended up being too high-level for me; very hard to follow, and the arising positions are oftentimes nontrivial to play, even if you have some prior experience in the Spanish; the Bc5 DOES make everything feel quite different.
If you do know stuff about the Ruy, have spent your share of time understanding what the Bc5 changes in "normal, untesting" positions compared to the Be7, and are a stronger player than myself (not very difficult, admittedly), I'm certain the theory itself is state of the art, though.
Svidler is extremely thorough and accurate - eg one line he went over later was played just the same in the Carlsen-Karjakin match, and he called it "You might hold this, but you won't have any fun" - which also happened (he instead recommends a different variation).
He is perfectly honest throughout, and clearly states where he couldn't find 100% equality, something that even books on the Ruggeldurb-Dingdong-Countergambit-System frequently refuse to do.
But yeah, it's less his thoughts on the opening, and more his moves in the opening