This is old stuff that you might have better luck finding in the library than in the bookstore -- but it's good old stuff.
Poul Anderson, World Without Stars is the perfect sf novel.
Larry Niven, The Trouble Twisters. Your sf alien collection is not complete until you've met Chee Lan, Adzel, and Muddlehead.
Larry Niven and Jerry Pournelle (co-authors) -- The Mote in God's Eye for aliens, Lucifer's Hammer if you want to see the movie that "Deep Impact" should have been.
Anything by Robert A. Heinlein -- his "kids" books are better than most so-called adult novels, and damn near all of his stuff is still in print.