I believe the most intricate plot won't matter much to readers if they don't care about the characters, especially in a series. So I try to focus hard on making each character, whether villain or hero, have an interesting flaw that readers can relate to.
“Ancient Rome was as confident of the immutability of its world and the continual expansion and improvement of the human lot as we are today.”
“Americans are opting out of public venues like the playground and the sidewalk for private venues like the healthclub and the mall. We're living our lives inside one form of corporation or another.”