Rebecca Keller (Wikipedia entry) has written, with the help of a few others, a series of science textbooks.  She has a PhD in Biophysical Chemistry.

Her Wikipedia entry lists the numerous books and textbooks she has written, and samples chapters for several of them are available on her website here.

Who uses Real Science-4-Kids?

Home schoolers in all 50 US states, as well as in Latin America, South America, Europe, New Zealand, Australia, Canada, Japan, and Korea, now use Real Science-4-Kids.  An active Yahoo group of 1,200+ maintains notes on the curriculum. In addition, a number of charter, private and public schools use RS4K.

Rebecca Keller interviewed

This episode of ID the Future features part two of an interview with Dr. Rebecca Keller, who discusses the nature of science and interpretation and how it applies to science education.