Only worth buying if you're a die hard Star Wars fan and love twitch-gaming.
Basically the entire game is broken up into different missions on various planets. Completing a mission grants you new Force Powers, which can be light or dark. After completing a certain number of missions, you have the choice of advancing the plot (which is thoroughly lame), which will result in more missions (yay!), or going back and completing the previous missions.
The combat is just like that of any other FPS (guns, grenades etc),...with the exception of the lightsaber - which the game is really about: Lightsaber combat is done in 3rd person real-time and is pretty manic stuff, never really giving you the impression of control that an elegant weapon from a more civilised age would. Instead, it degenerates into a click-fest. However there are various styles you can acquire over the course of the game (e.g double bladed , dual wielding, fast, strong etc).
Furthermore the game can get seriously frustrating as there's a lot of "jump here then there then over here in a this exact way in this exact time, then push that tile whilst pulling this lever". Oh, as for that choose your destiny bullcrap, there's really just one key moment pretty much right at the end, where you choose the Light or Dark path...which was outstandingly lame.
When all's said and done and if you insist on purchasing this game, only bother to select the Heal and Choke powers, as the others are pretty much a waste of time. When you have these two maxed out you can effectivley heal on the fly whilst tossing people off edges to their demise. Oh, and lighsaber combos/moves can be aesthetically pleasing if you can be bothered to get good with them.