This book published by the National Geographic Society, known usually for their factual accuracy, is beautiful in its pictorial content as other reviewers have said, but contains serious errors in the text. If you are thinking of buying for your 3-year-old, or your 5-year-old, they'll love the pictures and won't care about the mistakes. If you're contemplating buying it for your 6th grader's report on anything within the bounds of the solar system, don't.
The text on Mars states in its opening paragraph that Mars is the same size as Earth and is the planet nearest us. Wrong! Twice! In fact Mars is barely over 1/2 the diameter of Earth, and Venus orbits closer to Earth than Mars. (Diameters: Earth,7926 miles; Mars, 4221 miles. Because orbits are elliptical, distances vary, so averages are given. Orbit of Venus is about 35 million miles from Earth's, Mars orbit is an average of about 49 million miles from us.)
On the Mars page, the text does not agree with the chart or illustrations, which are correct.
The asteroid / dwarf planet Ceres is described as being "roughly equal to the size of our moon". Not even close! Sparing you the math, let's just say the Ceres is approximately 1/4 the size of our Moon. The text is again in disareement with its own charts. As before, the charts are correct, the text is in error.
Those mistakes were found just in browsing. Extensive examination may find more - but the errors above are enough to cast doubt on the rest of the book.
(Reviewer is a librarian, amateur astronomer, parent of 4, grandfather of 3.)