Sly Cooper and the Thevius Raccoonus is one of those games that despite it's few flaws, turns out to be a fantastic game
The premise of the game is very simple, and in the long run that's one of the main complaints with the game, that not only is it a little too simple and relatively easy, but it's also short. Sly clocks in somewhere at 6-8 hours of gameplay, as an estimate. The game comprises of 5 boss fights, each one following a series of levels sprawled across an adventure field, reminiscent of games like Sonic Adventure.
The levels themselves are fairly varied, even if they lack a certain challenge. The main goal of each one is to collect the key at the end, but also to collect a certain number of clues. Once all the clues are found in one level, you can open the safe found somewhere in that level. This usually results in some new ability to help Sly during his journey. The only real challenge in the early levels are the odd minigame type levels here in there, where you control a vehicle, or man a turret to defend one of Sly's friends.
However, once you get into the last section of the game the designers changed it up a bit. You no longer have an adventure field to explore with entrances to the various levels. Instead you go from one level to the next, with some very challenging platforming in between. This makes for a very hectic experience, which balances nicely with the somewhat lack of difficulty that the game is generally said to have by players.
Possibly the best part of Sly aside from the simple yet surprisingly fun gameplay, is the art style. The areas in the games tend to look like most games, albeit more colorful. However, the enemies and characters you meet, Sly included, are all animated really nicely in a cell-shaded style that turns out to be very appealing.
All in all, Sly Cooper and the Thevius Raccoonus is one of those games that despite it's few flaws, turns out to be a fantastic game experience.