First printing (1977 edition)
I read this book years ago and I still remember it clearly. Strange things are happening on the distant planets where, in the far future, mankind has scattered. Every planet has something oddly wrong with it. On one, people simply have no drive left; on another, the old rule the young; on yet a third, women rule men (yes, it's faintly sexist, but don't let that ruin a great book). A group of adventurers go from planet to planet, trying to find out what has caused this problem and barely escaping from each planet with their lives. Finally they make their way to old Earth... and what's going on _there_ makes all the messed-up planets look like paradises. Only in a great book like this could the statement of a mathematical formula make you gasp and drop the book. (Well, I did.) It's a shame that this book is out of print, but I strongly recommend that you find it somewhere!