A linear FPS with an okay story, but lacking gameplay depth and actual choices.
For example most of the augments in the game were useless. I never needed any of the hacking (beyond the augs that allowed me to hack into higher level computer systems), enemy detection, or radar augs and only started upgraded them when I had nothing good left to upgrade. Many of the upgrades such as being able to lift heavy boxes or survive falls were used more as gimmicks to reach secret areas than providing any real combat advantage.
Additionally some of the augs that seemed useful were completely useless like the silent walking aug which sucked primarily because you needed to manually activate it. If you wanted to use the silent walking aug with the cloaking aug in combination, manually activating both while dealing with a crappy energy system was horrific.
What was wrong with the energy system? Combined with very few items that refilled energy supplies, I found myself always low on battery power. Throughout 90% of the game I walked around with 1/5 batteries. With such a complete lack of energy to power augs, many augs were rarely used.
Augs aside, the worst part of the game was the linear boss battles. Apparently all of the bosses were outsourced to a different company who didn't know anything about the Deus Ex franchise. This poor decision is shown clearly with Human Revolution's very disappointing boss battles. In Deus Ex 1 you could pretty much sneak your way past bosses or use fun and intuitive ways to take down foes. Human Revolution throws this all out the window and turns bosses into a linear shooting fest. Not even your hand to hand combat abilities work on bosses either and most of the augs don't really help that much in detection.
As for the story, it was decent until the ending where you are literally given four buttons that choose your ending. I don't think it gets any worse than this. In fact this style of choice leads me to think that they threw it in at the very last second. Even worse I disagreed with the conclusions of all four choices, especially the second choice. The second choice honestly was the most reasonable, but I completely disagreed with the aftermath of that choice. Play the game to find out what I am talking about.
In conclusion the developers took a linear FPS and made it seem like an RPG with choices. It is clear that the team made a lot of cheap financial decisions. The boss battles were outsourced to another company. Who knows what other bad decisions they made. Ultimately Square-Enix banked on the Deus Ex name and got away with producing an utter pile of crap. If you remove the crappy augs and the broken dialogue tree system and the shoehorned ending choices at the end of the game, it's not an RPG, but an FPS that masquerades like a real Deus Ex sequel.