In Problems of Dostoevsky's Poetics, Mikhail Bakhtin makes an interesting point on ideas in literature when he calls Dostoevsky a "great artist of the idea." According to Bakhtin, Dostoevsky did have his own monologic ideas, and some of these ideas made their way into his novels. However, once in his novels, they became a part of the dialogic work. These ideas are not the author's ideological statements, but a part of the dialogic aesthetic of the polyphonic novel (and in Dostoevsky, these ideas are not separable from the character holding/speaking these ideas).
Essentially, Bakhtin makes a distinction between the way Dostoevsky as a thinker and Dostoevsky as an artist represented ideas. This distinction is between "straightforward monologically confirmed ideas," and what Bakhtin calls "images of ideas" or even "idea-images."
I accept this distinction, though it is not total (for example, Bakhtin shows that polyphony is a part of Dostoevsky's other writing, too). I also find it useful in understanding my own pleasure in reading in general, and my own pleasure in reading Dostoevsky.