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.
“I think that the only way to teach is by example, as children will more easily follow what they see you do than what you tell them to do.”
“Deciding to write a novel about something - as opposed to finding you are writing a novel around something - sounds to me like a good evocation of writer's block.”