Please support your local independent bookstore and order books from a place such as Warwick's or Yellow Book Road
Or find a store closer to you at IndieBound
Order from www.amazon.com or your favorite on-line source.
Order Harcourt books directly
Books are available in classroom sets from BookSource-- for example Wilma Unlimited
Audiobooks are available for the Lives of series, the Giants of Science series, and other titles.
Many titles are available as e-books.
For oldies but goodies, please check your library, order from your favorite out-of-print source, or contact the author at firstname.lastname@example.org