if you're a big fan of the show, go ahead, I'm sure you'll enjoy them.
the best (or, rather, the most interesting from a fan's perspective) of the two is After the Dark, mostly because it brings closure to the season 2 storyline (the wacky snake cult). Both are set after the events of Freak Nation (the season 2 finale turned into series finale), but ATD takes them a bit more far ahead and also brings resolution to the virus thing between Max and Logan.
Skin Game doesn't shake things much except for one character, while major stuff happens in ATD. It's basically a thriller, there's a serial killer to hunt for while the transgenics are still all inside Terminal City, surrounded by the Army and lots of people who wants them exterminated. I got the impression its bulk was written while the show still had a chance to have a third season.
ATD picks up a few months later, when that situation's been resolved and the transgenic have been more or less accepted as part of Seattle's population.
Both have a lot of action and are quite light on character study. In ATD Max kicks major ass. Have you read Before the Dawn (the prequel)? It's the same writer for all three, so if you liked his take on the characters the first time you shouldn't be disappointed. They're strictly fans only, though. You know what I mean.
There's a fourth book called the Eyes Only Dossier: it's a made-up (well, obviously) archive of four open cases Eyes Only was working on, it has fake emails, secret memos, interrogation transcripts, stuff like that. Difficult to describe but it's much more fun than the novels, honestly.