I am at last experiencing this adjective in full while enjoying "The Casual Vacancy" by J.K.Rowling. A superb gallery of characters vibrantly connected to one another. Great prose, raw and complex details in every day's comedy and tragedy. I don't mind exaggerating if I say there are even echoes of Shakespeare's clarity in painting clashes of feelings and wishes.
And maybe writing books for boys is the best trampoline for a good first novel for adults.
The best happens when the characters become close to you as friends. And once more you cannot but perceive the world as a stage.