One of a nice series from DK. I used several of these books for my autistic son, for whom fantasy and cartoon-style readers are not desirable. This series fits the bill: realistic art, clear explanations, and simple, big-print text.
Marie C. reviewed Diving Dolphin (DK Readers, Level 1: Beginning to Read) on + 337 more book reviews
Good reading. More like a level 2 though. 2-3 sentences per page.