The Complete Writer's Guide to Heroes and Heroines by Caro Lafever, Sue Viders, Tami D. Cowden (2000, Paperback)

Begin with Hero Archetypes and learn about the Chief or the Lost Soul or the Warrior. See what might make them tick.
Move to your Heroine Archetypes to visit with the Free Spirit, the Nurturer or my favorite the Spunky Kid. Learn how they got to be who they are.

Then you will learn how to use the Archetypes to Create Characters. As most writers understand, great characters are not one-dimensional and flawless. It is their layers that make them truly intriguing. Indiana Jones' fear of snakes made him believable.

Finally play with Archetype Interactions and see how the Waif might react to the Professor type. What if the Waif were layered with the Librarian and the Professor had a bit of the Swashbuckler in him. What would these two encounter? Where would they take your story?

Tami et al's book is invaluable to me. If I had no other book on characterization, I would be fine. My only quibble is that we didn't get the Villains, but Tami teaches a Villains Archetype class online as well as face-to-face. I just recently had the pleasure of taking that class with From The Heart Romance Writers.

Put this on your "must have" list if you want rich, complex characters.