The best portions of this book are hands down the Class chapter followed by feats, spells, and items (pretty much in order). I thoroughly enjoyed vigilante as a class during the playtest and love it just as much now. I know that this class is not a good option in any sense for normal adventuring; however, for certain adventures vigilante comes out swinging.
Feats are mixed for me. Some run into the problem of feat taxes while a couple feats seem to be a different approach to a previously released feat.
Spells and items were mostly a gloss-over for me. Each spell and item aides players in different aspects as expected. There were not really anything in these sections that screamed to me a "must have" for my next character. Some spells also come off as being able to ruin a GMs plan. Not because they are powerful. Rather these few spells are like skipping a few chapters ahead in a book because your need to know outways your interest in the story. With spoilers about the latest shows and movies posted EVERYWHERE, spells like greater detect magic are a painful reminder.
Finally, the new mechanics presented within this book are... okay. They serve as nice suggestions and advice for experienced GMs and players. A new GM trying to implement the expanded mechanics found in chapters 3 and 4 might struggle to assign DCs and putting together an appropriate challenge. I think these sections could have included fuller examples at the very least for new GMs; just something to model after.
The book scores about average for me (65 out of 100 points). This is definitely the weakest book in the Ultimate line, but still worth adding to a collection (at least in pdf form).
For a full review and how I determined my score: Ultimate Intrigue Product Review.