Silver Spring's Valerie Tripp is mom to Felicity, Josefina, Samantha, Kit, Nellie and Molly. If you think that means she has a full house, think again. The girls don't have their own rooms; instead they share one upstairs room where they live out their adventures. You see, Valerie Tripp is the author of most of the American Girl books, and the girls mostly live in her head and her office.

Tripp, who has been writing books for kids for 30 years, figures she has written about 35 American Girl books, which tell how girls lived in different historical periods. In addition to the books, there are American Girl dolls, jewelry and now a made-for-TV movie (coming this fall) that features Samantha.

Valerie Tripp recently spoke to Tracy Grant about where she gets her ideas, how she does her research and whether boys read American Girl books.

How did you get started writing American Girl books?

Right out of college I wanted to work in publishing because I thought they'd ask me to read books all day and I thought that would be fun. From 1974 to 1981 I worked writing stories with very tight rules on the phonics I could use [for example, no words with long vowels!]. The author of that series was Pleasant Rowland. Some of the stories I wrote got put aside, including some that were historical fiction. Then in 1983 Pleasant called me up with this idea about doing books, dolls and clothing set around these historical fiction stories I had written. I got to help plan all the characters and pick the character I first wanted to write about, so I picked Molly [who lives during World II].

The series is called American Girl, but do boys read your books?

I have a lot of boy readers. A lot of them write to me and say they can identify with the boy characters. Some of my favorite characters are the boys, who offer contrast to the girl characters because they have more freedom. Boys also like the history in the books.

What comes first, the books or the dolls?

It works both ways. Sometimes I'll say [to the person creating the doll], "Kit has to have a typewriter because she wants to be a reporter." Sometimes a product designer will say, "I found the most amazing telescope. Can you write it into the book?"

How long does it take you to write an American Girl book?

I research for about half a year and then I'll write the arc [outline] of a girl's six stories [each character's story is told over six books]. It takes me about two years to write all six books. There's a lot of rewriting. The hardest thing for me is to make a story look smooth and straightforward. That's what rewriting does for me. I prune away all the extras . . . and stick to the strongest, best parts of the branch. But I always keep what I prune away because it might be good in another story.