How did the books affect the way you look at the characters present in the games?

Do the comics count, or are you only counting the novels?

Also, does the order matter, as in which story you experienced first, or the particular medium the character(s) originated in?

Speaking only for myself, I only got around to reading the initial books by David Gaider and Patrick Weekes, and only skimmed Nunzio DeFilippis and Christina Weir's comics. So feel free to take any of my comments with a grain of salt.

To me, everyone's personalities in Gaider's stories felt more or less in character along with their video game counterparts, with one major exception in Isabella's case. The revelation that she just screamed "drama for drama's sake", as if she didn't have enough already. The whole thing pulled me out of the story and I couldn't take it seriously.

By contrast, Weekes' Cole was so divorced in tone from Gaider's that I don't know why they didn’t just create a new Spirit of Compassion for whatever character concepts they wanted to explore. Even more frustrating is how they wrote and later ruined Briala; the woman in THE MASKED EMPIRE finally freed herself from Celine's clutches, so it made ZERO sense for her to not inform the Inquisition of the Empress' murder of her parents or the genocide of Halamshiral's alienage. If Weekes was really so inent on repairing Bioware's "lesbian betrayal" cliche, then they should have had Briala move on to a better woman, instead of allowing players to reunite her with her abuser. So when in comes to maintaining internal consistency and character development, Patrick Weekes' interpretations are in my eyes, pardon the pun, weaker overall.

Sadly, you're right. We have to work extra hard to come up with a reason to let Celene die (and pay for Halamshiral) 

I haven't read any books and or comics since to me if anything from them was not relevant if they were they would have been in game so to me they were time killer while waiting for the next game while filling in the blanks and *cough* aiding in revenue for the writers.