If Carol Cassella had her way, you would not be able to buy a copy today of her new novel, Healer.

Not today, and maybe not any time soon.

“I really had to struggle to discover the heart of this story,” Cassella told me over a recent lunch at the Treehouse on Bainbridge Island. “I started out with such a clear idea of where the plot should go, but the characters I was developing and the emotional impact I was going for kept taking me in a different direction.

“Writing it was a very difficult two years. Just before my deadline, I wanted to rewrite it as a whole different story. But then I had to turn it in to my publisher.”

That being said, Cassella’s editor was happy with what she turned in.

“And sometimes the editor sees that way before the author does,” she said.

And that being said, Cassella had good reasons for her second-novel jitters.

Healer, much like Oxygen before it, started as a medical mystery — almost a genre exercise, she said. Cassella, an anesthesiologist at Virginia Mason Medical Center in Seattle, started it when she found herself intrigued by the shadowy world of big money and biotech research. But while Oxygen dwelled in a world she intimately knew — her main character was an anesthesiologist, after all, and the story was split between Seattle and her native Texas — Healer dragged Cassella far out of her self-confessed comfort zone.

For one, the story is set in a fictional Eastern Washington town (basically, a stand-in for one of the more touristy villages in the Methow Valley). For another, Cassella may be a physician, but she said that going into the writing of Healer, the biotech world was as big a mystery to her as it probably is to you or me. Three, the narrator is a doctor who gave up medicine fifteen years before, and because she lacks board certifications, works in a small clinic that handles migrant laborers on a sliding scale. Cassella, by contrast, still works (albeit part-time), and today — release day — is just another day in a white lab coat for her.

More about the story: Claire Boehning, at 43, sees her upscale Seattle world turn upside-down when her biotech-researcher husband, Addison, loses all his venture and personal capital to a gamble on an anti-cancer drug that flunks its early trials. The couple, who have a 14-year-old daughter, are broke. They sell their tony home on Lake Washington and retreat to their ramshackle second home in the tiny town of Hallam. Faced with a looming inability to pay even the most baseline of bills, Claire hauls her medical license out of mothballs. But all she finds is a job of last resort, at a clinic run by an aging, ailing and overworked old doctor. Meanwhile, Addison is desperately traveling the country, meeting with venture capitalists, trying to revive interest in a drug he’s convinced was unfairly derailed. Suspense looms over some big questions: Was the drug flawed, or were the trials flawed? Will big money trump big science? Will some key characters do the easy thing … or the right thing?

As readers of Oxygen know, Cassella doesn’t tilt toward happily-ever-after endings. Nor does she fatalistically throw up her hands in the face of what seems like an impenetrable ethical and moral quagmire. What usually happens in her work, just as in real life, is a tense and deliberate detangling of some serious gray areas. And so, in a sense, the mystery that Cassella said she started out to write remains intact after all.

“I may have started out one way, but I never wanted to write just a black-and-white story,” Cassella said. “I find that the gray zone is a far more interesting place.”

Finding her gray zone came through years of craft development, much of it through Bainbridge’s Field’s End and critique partners in the author community around Kitsap County. As difficult as Healer was to finish, the making of Oxygen, Cassella makes clear, was much longer and harder. She started as one of probably a zillion people in middle age who wanted to write, but had no idea what … or how.

“If you get to midlife and you’re not going to buy a Ferrari or argue the bigger questions, you’ve got to do something,” she said with a smile. “It became obvious that I had to write because I wasn’t going to stop beating myself up for not writing.”

That said, Cassella was generally happy in her career and in her family life, as a wife and mother of two sets of twins, ages 14 and 15. And her motivation for writing at the time was to finish a book so she could say that she’d finished a book … and then put it on a shelf. “I wanted to write, but everything else got in the way. Like folding laundry,” she said. “I learned that I couldn’t wait for time to write. I had to make time to write.”

But, with the encouragement of author friends, she spent three years writing the book, and used Oxygen to shop for an agent, and after that, a publisher. There were rejections along the way, but the book found its home, and continues to be a big success over two years after its release. It’s had about 10 foreign translations, and just recently made a big splash in Canada as Wal-Mart’s “Read Of The Month” up there.

The book’s success meant that Cassella, soft-spoken in person, had to develop a public persona for signing and touring. “It’s not in my natural grain,” she admitted.

But, like thousands of other authors who have likely said the same, she’s found her way. And Kitsapers can see for themselves when Cassella appears 3 p.m. Sunday at Eagle Harbor Book Company to read from Healer and sign copies. (She’s also appearing at 7 p.m. Thursday at Elliott Bay Books in Seattle.) After that, she hits the road out of state for nearly three weeks before making some more stops at bookstores up and down Puget Sound. (Click here for her schedule.)

And then it’s back to work on book No. 3, already in progress.

“My next book will be a medical mystery, about a woman who’s a doctor,” she said. But then she hastens to add: “It’ll have different voices, a different feel and a different theme.”

Just like Healer does. Oxygen it isn’t. And while I’m no critic, I’m confident in saying that it, like the book itself, is a good thing.

Even if Cassella isn’t quite able to admit that yet.