I work in a bookstore. I have found it difficult to find quality sf books for younger readers. Most of what is being published is fantasy. No Limits is a great resource for teachers, parents, librarians, and anyone interested in helping a younger reader branch out and enjoy SF. Julie Czerneda shows that SF can be educational as well as entertaining. Her companion book, Packing Fractions, contains the stories discussed in No Limits. I've used these two books with my niece, age 13. She is now an avid SF reader, and actually prefers reading to watching television!