Robert Heinlein wrote some really good stuff (before becoming increasingly erratic in his later years). Very entertaining and fun. Here are some that I would recommend for starting out with:

Tunnel in the Sky. The opposite of Lord of the Flies. Some people are stuck on a wild planet by accident, and instead of having civilization collapse, they start out disorganized and form a civilization because it's a good idea. After reading this, I no longer have any patience for people who claim that our natural state is barbarism.

Citizen of the Galaxy. I can't really summarize this one, but it's got some good characters in it.

Between Planets. Our protagonist finds himself in the middle of a revolution all of a sudden. This was written before we knew that Venus was not habitable.

I was raised on this stuff. Also, I'd like to recommend Startide Rising, by David Brin, and its sequel The Uplift War. They're technically part of a trilogy, but reading the first book (Sundiver) is completely unnecessary. It's not really light reading, but it's entertaining and interesting.