This website offers a wide range of fiction and non-fiction e-books from Pre-K-up. Be sure to use the drop down filters to find the appropriate grade & type of book you are looking for. Note: most of these books WILL NOT have Reading Counts quizzes.
Junior Library Guild offers 30-50 titles of e-books per month. The selections on this digital platform change regularly so check back for new titles! The downside to this site is that you can't really filter by grade or type, but all are appropriate for elementary students. There is a good chance many of these books WILL have Reading Counts quizzes. Be sure to check the titlehere.
Non-fiction interactive e-books for grades K-5. As you scroll through, you will notice that they are arranged alphabetically by category and then reading & interest level with earlier reading & interest levels listed first. The upper elementary categories are listed after all of the lower elementary categories.
Check out what your local library has to offer online! You will probably need to create an account in order to check out most of these e-books. The public library website also offers additional links and resources.