They're just illustrated versions of the books. I'm a big fan of a lot of the Forgotten Realms books, and especially Salvatore's stuff, the comic versions left me a little cold. They're not really bad, but they don't really do justice to Salvatore's amazing fight scenes, and they translated the books a little too literally, directly lifting dialogue and such. This tends to make the comics feel very rushed.
Now, if you want some good, lesser-known fantasy comics left me recommend the following;Rokkin: A six-part mini-series from Wildstorm that just concluded. It's absolutely filled with crazy amounts of swordplay, disembowelments, and over-the-top action. It focuses primarily upon Arness, a butcher-turned-slave who, through selfless actions, earns the favor of a divine deity, which allows him to become Rokkin, a powerful warrior covered in stone. It's all sort of tongue in cheek, and one of the best fantasy comics I've read lately.Knights of the Dinner Table: Illustrated: A spinoff of the popular Knights of the Dinner Table comic (once featured in Dragon Magazine), this comic parodies traditional pen and paper RPG gameplay. The first several issues, drawn by Aaron Williams (Nodwick), are just awesome.
Kenzer and Company (who publish KODT), also did some Dungeons and Dragons comics years back that, if you can get ahold of them, are awfully good. I was a big fan of In Shadows of Dragons.
Also good are Nodwick, which is available online and in trades, and Girl Genius.