Cassandra Carter is one to make you think, “Hmm . . . what the heck was I doing with my teenage years?”

The 18-year-old’s own reply involves a nationally published book and two more in the works.

Her debut novel, “Fast Life,” was published in July as part of the “Tru” series from Kimani Press, a division of Harlequin that focuses on African-American young-adult fiction.

Carter started the book when she was just 14, after getting the idea from, of all places, a dream.

“I woke up and – I hate telling people this because it makes me sound crazy – but I heard a voice . . . saying, ‘Cassandra, you should write a book about that.’ So I created this character. It was about this girl and she’s . . . got to go and move real quick, and everything else just kind of came.”

There’s a lot of “everything else,” since the move is over in the first 50 pages. What follows is a fast- talking, high-rolling rumble following Kyra Jones between Chicago and an island in the Bahamas, complete with gorgeous guys, sniping girls, friendships gone horribly bad, scandalous wealth, the illegal drug industry and a few more page-turners.

Carter worked on it all through the summer she was 15, and when it was done she mentioned it to her grandmother, Sandee Grassi.

“I wasn’t at all surprised,” Grassi said. “Cassandra has always impressed me with her dream of and enthusiasm for writing.”

Grassi encouraged her to get it published, but Carter balked: “She was afraid it would change (the family’s) opinion about her or that people might think the book was about her life. But hey, it’s a book and it’s fiction – now, someone’s got to read it, right?”

Grassi talked her into at least taking it to an uncle in the book business, though Carter was still nervous.

“He’s a blunt person, and I thought, ‘Oh, my God, what is he going to think?’ ” she said.

He thought it was a darn fine book. He passed it along to a friend who was a literary agent who ended up taking Carter on as a client.

She’s still taken a little aback by the book’s success. The online reviews at both Amazon.com and Barnes and Noble’s Web site have been overwhelmingly positive, and the comments on her MySpace page are fairly bursting with praise.

“This is so surreal almost, sometimes, like going online to look myself up, and having people contact me telling me they like my art and my book,” she said.

She’s finished her second book, “16 Isn’t Always Sweet,” which is due for publication in March, and is working on a sequel to “Fast Life.”

“I’m excited to work on it. I’ve even thought about carrying (Kyra Jones) on through a series. . . . I’ve started planning things that happen to her in, like, volume 5. Trust me, I have a million ideas. I just need the time to sit there and get ‘em out, that’s all.”

And it’s time that she’s taking. Even though she graduated from Huron High a semester early with honors in January, she’s decided to put off college for a while and give this dream some hot pursuit.

“I know it’s such a risk putting school off the way I am, and it weighs on me. . . . They say that people who are successful at creative ventures like this are the ones who’ve been doing it since they were born, and that’s me right there, so I’m willing to take the risk.”