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.
“In arriving at a decision in a question of doubt, the apostles in the Acts were guided solely by their sense of the Spirit behind the action, not by any speculations as to consequences which might ensue. And so they found the truth.”