Most novels are written using a three-act structure and trilogies fit nicely with the structure of most novels. Shakespeare sometimes used four acts, but three seems to be the magic number when wrapping up a story and plot—it also seems to be the magic number when wrapping up a story arc as well. We can get the meat of the protagonist's past from the first book in the trilogy, ending with somekind of action. Book two can be action packed, then we find resolution and conclusion in most respects to theme and plot in book three of a trilogy.
My upcoming series the Deeps will consist of three books, no more and no less, and it too will follow the three act tradition: each book will have its own discrete characters, storyline and plot, but the series will carry a larger story arc I hope you'll enjoy. Set in Regency England and Nepolionic France, and told from a female protagonist's point of view. It's got plenty of strange Regency style goings on and gothic horror thrown in—for a dash of pleasure. I'm hoping you'll enjoy the series.
Here's a picture I took of a canal at a local park. I hope you like it and would love to hear comments. I plan to use it for the book's cover.
You can find me through the week at www.Kimwelsman.ca or on twitter @kimwelsman.