I didn't realize when I started reading it that it was such an older book, so it was slowly unveiling information that is now pretty common knowledge. That aside, the reason I give it only 3 stars is that I felt like it was written for a small child. The subject manner was definitely advanced and worth reading, but the style in which it was written reminded me of an enthusiastic preschool teacher. Wow! What's next?! Gasp! What does that mean? Children, that means..... and so forth. You get the picture. I felt patronized and annoyed. The last of the book was about the Kuiper belt, but it was so agonizing I couldn't finish it. The Kuiper belt is well known now, even if not a lot is known about it, and there are actually ice dwarfs that are larger than Pluto, but at the time of this book it was astonishing, I guess. The authors toyed around and hinted and wowed and I already knew what their big surprise was so I stopped. So, all in all, the info on the early research on Pluto and the scientists that conducted it was interesting. The style it was delivered was annoying. The 'current' information was old so I didn't read the last chapter. ( )