Fangs! is an appealing non-fiction series for preschoolers through 1st graders, particularly for reluctant young boy readers. The text is larger than most books and is composed in short sentences, usually about 3.
True or False series by Melvin and Gilda Berger is a young science series in a fun question-and-answer format. My kids reviewed Storms and Birds and gave both a thumbs up. For ages 6-9.