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.
“You can't just ask customers what they want and then try to give that to them. By the time you get it built, they'll want something new.”
“I mean, the things you think will never happen, you have to confront; those things that come into your life that you thought you never could deal with, you do.”