Is that as far as you watched? I personally thought the story got a bit lame from there (I also stopped watching Gurren Lagann at the start of the Anti-Spiral arc; fuck that shit), but I'll summarize it for you.
Several years pass by after L dies. Replaced by L is Near, a much younger prodigy from the same orphanage as L who is obsessed with stuff like epic card houses (if you watch it, you'll see what I mean). Mello is offered to work alongside Near to catch Kira, but insists he'll do it his own way -- and by that, I mean he joins the mafia and sits around eating chocolate all day while taking Light's sister hostage to obtain the Death Note.
Meanwhile, Light becomes the chief of the Kira investigation unit, and decides that it's too risky to be using the Death Note himself (I forget why and if this happened before L died, but he also pretty much gets Misa to ditch her Death Note), so instead, he gets Kira support Teru Mikami to do it for him. Many chants of "sakujo" echo through Mikami's room on a daily basis when he receives the Death Note. He also persuades a popular news reporter (Kiyomi Takada) who had a crush on him during their college years or something to support Kira in her work.
Long story short, Light's dad dies, his sister becomes permanently tramautized by her kidnapping, and his mother becomes severely depressed by all this. Mello dies after kidnapping Takada, and Takada is killed off by Light to cover things up. Mikami becomes a suspect, fucks up, and ends up causing Light to get exposed when Near's group meets with Light's group in a warehouse. Light gets shot up when he tries to use a Death Note piece hidden in his watch, and drags himself around the surrounding area for a bit before Ryuk makes some speech about how they had fun and shit and writes Light's name in his Death Note.