While working on each of my previous six novels, I assumed it was either the only or the last story I’d ever write. Even follow-on books like Children of God and Epitaph came as a surprise to me. So I’m amazed to find that I’ve begun to do the research for an eighth novel.

I am still immersed in writing Number Seven. Unremembered Lives is now a little over the halfway point. Ordinarily, 175 pages would be a long enough sample for my agency (Dystel, Goderich and Bourret) to offer publishers, but for any author, every new book is a separate roll of the dice. Even if you write a series with the same characters, each addition to the pile might be the one where readers figure out your formula and get bored, with a subsequent fall in sales.

I routinely jump genres and styles and topics, which makes every new book a gamble for me, the agency, and a publisher. Given the current political upheaval, I’m not sure if a novel about the early American labor movement will be thrillingly topical or dead in the water when it eventually goes out for consideration.

So far, my test readers seem genuinely enthusiastic about Unremembered Lives, but I plan to complete it before my agency tries to place it. At the very least, waiting to shop it around will decrease the probability that an acquiring editor will die or quit or get fired or leave the industry before I can finish a novel.

In the meantime, I seem to be coping with my anxiety about all this by indulging a lifelong interest in something that might develop into another book.

I’ve been fascinated by the family of Henry II since Peter O’Toole starred in “Becket”  and then in “Lion in Winter.” And I love Shakespeare’s histories as well, particularly Kevin Branagh’s “Henry V” and Ben Wishaw in “Richard II.”

I’ve never quite understood what the War of the Roses was about and why England and France are so enmeshed. I was already trying to figure that out when the History Channel’s “Vikings” series brought us up to the point where Rolo’s Vikings became France’s Normans.

I decided it was time to connect the dots for Western European history after the fall of the Roman Empire. I began sorting out various barbarian hordes and was surprised by how influential the Vikings were in the development of the modern nation-state. I’m pretty sure I now have all the big pieces connected, including the Norman Conquest of England and why Plantagenet kings kept invading France.

This was all just personal curiosity until I got to a biography of the knight William Marshal — a medieval Zelig.

He died in his 70s, having known and served everyone in “The Lion in Winter” cast: Henry II, Eleanor of Aquitaine, Richard the Lionheart, Philip Augustus of France, and John Lackland, who lost all of England’s French territories.

William Marshal not only prevailed upon King John to sign the Magna Carta, it was he who was called upon to decide if England would remain separate from France or return to the fold after John died without a clear heir to the throne. We speak English because of his decision.

I’ve considered two ways into this story. I might have done a series of chapters focused on Eleanor of Aquitaine, each of which would take place during a Christmas Court when the Plantagenets came together, whether they liked one another or not. Mostly not.

Eleanor’s death would truncate the story before I get to William Marshall’s final days. It’s always useful to have a Point of View character who is insightful and knowledgeable about the other characters — particularly one who’s got skin in a dangerous game. So now I’m thinking it would be interesting to create a readable but period-sensitive narrative by Marshal himself. We’ll see…