Oh hey, L5R! I assume you're talking more about the CCG than the RPG (which is also good). Anyway, I'm a few years out of the loop and never really got into the tourney scene so consider me a sketchy source here. That said though...

It's a really solid game. I'd say second only to Magic as far as CCGs go, and to my knowledge, any card ever printed is still totally fair game. New sets don't reinvent the wheel mechanically, they just progress things plot wise.

As in, every year they have a big ol' tournament, with the developers watching how the last few games play out. If Clan X comes out on top, the fluff of the next set says their leader is the new emperor. If there's a big duel between two characters, one kills the other. If someone wins by mixing some naga cards into his deck? That clan allies with the naga. Stuff like that.

This leads to multiple versions of the same character, but you're free to use any or all. You can promote a character to a version of that character from a later set as an alternate method of getting them into play.

Past that, there are, if I recall, 3 ways to win- There's actual cards of the 5 rings you can get out, but doing so is a royal pain, so that almost never happens. There's successfully attacking all 4 of your opponents Holding cards (kind of a combination of life points/secondary hand containing all your land-equivalent cards, to really stretch a metaphor), and there's getting up to 40 honor points, which, in my experience, is the most common victory method, since a lot of things rack armor up, particularly winning a fight.

Attacks are big productions that don't get made until pretty late in the game generally. There's a ton of buildup until someone feels confident that they can win and makes a major attack, and then you spend a good 5 minutes or so activating special abilities, playing cards, challenging characters to duels, feels like you've actually got some huge crazy war scene playing out.

As far as getting into it... work out which clan has the most appeal to you, grab a starter deck of it from the current set.
http://www.l5r.com/the-clans/

Is the ban message any good? I could use a laugh.