How you use free third-grade books that are available online depends on your purpose. You can use free online books for home schooling, tutoring or pleasure reading.
Most books that are available for free online are considered public domain, meaning that the book has passed its copyright date. Many children's literary classics are public domain and can work for home schooling and pleasure reading alike. Some public domain literary classics include "Adventures of Huckleberry Finn," "Alice's Adventure's in Wonderland," "The Jungle Book" and "Robin Hood." These books are available from the Library of Congress, and readers can access them online or download them as PDF files.
Sometimes, old editions of textbooks are available for free through the publisher's website. A home school or tutoring program could use a free edition of a textbook by pairing exercises and assignments with chapters of literary books.
Self-published e-books may also be free. When selecting an e-book to use for educational purposes, be sure to consider the credibility of the author. Check the author's credentials to make sure he has expertise in the subject area the e-book focuses on. E-books often provide useful supplementary materials, such as daily activities and exercises, to use in conjunction with curriculum from a textbook.