The Calling starts off with an excellent plot hook. One of the Gray Wardens (warriors tasked with keeping a lid on the Darkspawn threat) has been captured by the enemy and taken deep underground. This particular Warden has knowledge that the enemy could use to launch an assault and potentially even destroy civilization entirely. The other Wardens decide that they must breach the underground realm of the Darkspawn and either rescue or kill the captive before he can reveal this knowledge. Sounds pretty ominous.
Yet, the novel stumbles almost immediately by the bizarre decision to include probably the least interesting character from The Stolen Throne in this mission, the generic good-natured "nice guy" Maric who was thrust all unprepared into leading the rebellion and later becoming the King of Ferelden. The rationale for including this fellow in the story is poor at best, and his presence as the spotlight character steals time and attention from the interactions of the new main characters. David Gaider's treatment of Maric in this novel virtually turns him into a Canon Sue--except that Maric is portrayed as "endearingly" incompetent except in the realm of getting people to like him. He was only tolerable as a character in The Stolen Throne with the cynical and harsh Loghain to balance him. In The Calling he is tedious. The multiple re-treads of his romance with Katriel in the first novel (especially since he finds a new elf chick to glom onto) inspire epic amounts of eye-rolling.
This is sad, because the story itself is quite interesting and raises a lot of questions about the setting. Are the Darkspawn directed by a conscious evil, or are they merely animals driven by inescapable instincts? What, exactly, are the motivations of the mysterious Architect and are they benevolent or horrific? What is the nature of the Old Gods and this strange relationship they have with the Darkspawn? Yet these questions and their impact are largely minimized by excessive attention to Maric's personal problems and a return to the "setting tour" in the form of basically unnecessary battles with a dragon and an abomination. A couple of editing missteps (you could make a drinking game from the number of times the words "a single bead of sweat" and "sickening crunch" appear in the novel) seal The Calling's position as a solid meh.