On the face of it this book is best suited to children up to 7 years old... but it really has a lot to offer ANYONE who doesn't know what the nine planets are and where they are in relation to the sun! My son (almost 8) found it a great read, although he did comment that it wasn't 'exactly' like a 'proper' Dr Seuss... almost though... he still loves it.
I then took it into work where it was well received and two colleagues had learned their planets by the end of lunchtime. Great fun! I'd also recommend 'Inside Your Outside', also by Tish Rabe, we loved it