I'm looking for recommendations for the best hard science fiction novels about space travel, exploration and colonizing new planets. What I'm looking for are novels which explore current scientific theory about space travel and exploration. I'd also like to find books that explore the most likely solar systems and planets that scientists have found where human life may be able to live. I'd like to find novels in the nearer future about the initiation of space exploration and planet colonization not novels that take place in the very far future when the planets have already been colonized by humans. I'm currently reading the Mars trilogy books by Kim Stanley Robinson. They're very good, but I'm looking for books that explore further solar systems and more Earth-like planets. What technology is needed to get to these planets? What are these planets like theoretically? What types of lifeforms may be found there? Any recommendations of books that fit this description would be greatly appreciated.