Robert Anson Heinlein. Stranger in a Strange Land was great, as was The Moon is a Harsh Mistress.
"An armed society is a polite society. Manners are good when one may have to back up his acts with his life." - Beyond This Horizon
"I also think there are prices too high to pay to save the United States. Conscription is one of them. Conscription is slavery, and I don't think that any people or nation has a right to save itself at the price of slavery for anyone, no matter what name it is called. We have had the draft for twenty years now; I think this is shameful.
If a country can't save itself through the volunteer service of its own free people, then I say : Let the damned thing go down the drain!"
Ahem. Fuck Roosevelt! :)
Occasionally I read sci-fi, or what passes for close to it. I recently read 'The Stars My Destination' by Alfred Bester, whom some consider a god-father to the genre. It was originally released as 'Tiger, Tiger'. Also enjoy the classics, like Asimov, but also like Richard Matheson and some of Vonnegut's science-fictiony (?)
I've got Amazon on hold while I look at other's suggestions.
I agree with that view of Asimov, one of my little quibbles. I'm not actually very fond of his characters in general, I like his ideas & plots, but his characters and style are not my favorite. I enjoy his essays sometimes more than his fiction.
If you want to read a very different style than Asimov, Ruddy Rucker goes into quite a bit of detail about how the created characters feel and think about themselves and their lives - he focuses quite a lot on on both mechanical and biological artificial life forms. I'm not crazy about his human characters, but his style is crudely energetic cyber punk that can be fun; you might like it if you like Amy Thompson, since they are both considered to be "cyberpunk" for what that's worth.
George R. R. Martin; Octavia Butler; Katherine Kurtz
Fritz Leiber is generally considered to be an fantasy rather than sci-fi author, but I like his stuff both for being well crafted, humanistic with amusing characters and commentary on the human condition, and it's sometimes called "crudely vulgar and anti-Christian" which are not bad things in my book.
I'm also a huge fan of Stanislaw Lem - to me he reads like Vonnegut in that he seems to have a profound grasp of human nature at it best and worst, but with a bit more hard science elements in the mix. I also love both authors for their humor, and their willingness to be all kinds of funny - silly, goofy, surreal, bizarre, darkly funny / gallows humor, sly, childish, but then by turns crushingly tragic and heartrending.