What makes this so highly rated? Please be specific.

Reviewers aren't paid off, but to stay above water any popular gaming publication needs access to games before the general public. With advance copies, it can tell readers whether or not to buy before launch day rolls around. Without it, they're stuck reviewing after the fact and they're not going to get as high traffic. I doubt there was any particular pressure on reviewers to review this game, specifically, well, but it's not a good business practice to piss off the companies you're relying on to send you free, advanced copies of their games by pissing over said free, advanced copies of their games. Review scores tend to be high in general for this reason. There's a reason Yahtzee spent months only reviewing games that have already hit stores. (Not sure if he gets advanced copies now or not, but if he does I'm going to argue that he's the exception to the rule.) As for why this game is universally liked, I'm going to assume it's because: 1) The blending of platformer/action adventure/FPS mechanics is done seamlessly. 2) The game can be challenging along the lines of an FPS/hacknslash (how well can you kill all the guards) and/or a strategy level (finding the best way to sneak past everyone undetected). 3) The world is developed unobtrusively and deeply, without needing to rely on direct exposition/NPC dialogue: the codexes are actually gripping and believably written, etc. IMO the Heart is done brilliantly, best way to explore the story of a world I've seen in a long time. I killed 10 minutes after the tutorial level just hearing all the secrets about the people in the bar, and the bar itself. 4) The aesthetics of the game is unique and high quality. Likewise, the world of the game is unique in its composition, if not in its individual parts. 5) Players truly have the option to accomplish goals in however they see fit, in everything from how they move around the map to how they interact with NPCs to which way they choose to end their targets. Other games purport to give you "choice" (looking at you, Bioware) but tend to give you the /illusion/ of choice, or the "choice" of 1 of 2 different dialogue options leading to however many different cutscenes. This game actually allows you to pick what you're going to do on every single level, from gameplay to tactics to storyline.