The Worldwar series by Harry Turtledove is fantastic.

And if you like humourous books, you can't go wrong with The Hitchiker's Guide To the Galaxy.

Hope that helps.

The Stars My Destination (also known as Tiger, Tiger) from Alfred Bester is among the best I ever read and its a rather short one so you should really read it

Stranger in a Strange Land and The Moon is a harsh Mistress from Robert A. Heinlein are also really good.

Childhoods End is one of the best books from Arthur C. Clarke and if you like his style you should definitely read all four books of the Rama series : Rendezvous with Rama, Rama II, The Garden of Rama and Rama Revealed (actually it might be better to skip the first one as many find it rather boring but the others are totally awesome. Space Odyssey 2001, 2010, 2061 and 3001 and the three time odyssey books (Time's Eye, Sunstorm, Firstborn) are also great

If you prefer short stories I suggest those from Stanislaw Lem many of them are humourous (especially The Star Diaries) but also very philosophical. Solaris from Lem is also a good read but very philosophical so if you aren't into that stick to the short stories or his humourous books like The Futurological Congress (a total must read) and Peace on Earth. (I don't know the english translations of them, but I hope they are good)

I personally never enjoyed the books from Isaac Asimov very much but you might like them. Only book of him I'd suggest myself is End of Eternity

I suggest reading the first 10 pages of a book before buying it to see if you like the style of the author. If you tell us what books you read already and which you liked and which you didn't like we'd be able to give you a bit more specific hints.

I really enjoyed The Dark Wing by Walter Hunt (I got my copy signed), it is a series. I also really enjoyed the first 4 books of the Horus Heresy, which are novels set in the Warhammer 40,000 universe. I am currently reading the 5th one, but it gets off track and from what I hear the next few books don't even talk about the Heresy... Also for more 40k reading the Blood Angels books were really good (the author wrote the 4th Heresy book too)

The Lost Fleet Series by Jack Campbell is one of my favourites

The Seafort Saga in six volumes by David Feintuch. A modern day interpretation of the chronicals of Horatio Hornblower set in the distant furture of space.

The Posleen Series by John Ringo...Think billions of aliens invading earth, the average one is dumb as a box of rock but mean as a pit bull.  Also if you would like some fiction that closely resembles SOASE ...The Shiva Option, complete with choke points and warp lines! If you are however in the mood for something epic, try Pandora's Star by Peter F. Hamilton.

I'm probably going to get flamed for this, but I've always enjoyed David Drake's RCN series(With the lightnings, Lt. Leary Commanding, The Far Side of the Stars, The Way to Glory,Some Golden Harbor,When The Tide Rises).

It's set in a relatively low tech universe where machinery often breaks down and space travel is sometimes dangerous and unpredictable in much the same manner as oceanic voyages in the age of sail.

There are graphic descripitions of deaths in battle in this series and it's obviously not for everyone. It isn't just gore for the sake of gore though. One of the reacurring themes in the series is the guilt many of the characters deal with over taking the lives of other human beings in the line of duty and this is a point that would be hard to get across without describing exactly how horrible the actions they had to take were.

Because of the level of violence in his work the author is often accussed of advocating war, or of writing "military pornography", but I personally feel that the graphic depictions of combat in his work is alot less desensitizing then works in which entire fleets are blowns to dust without any mention of the fates of those who were aboard them at the time.

In short, the books are full of realistic characters and thrilling, swashbuckling adventure in a sort of "age of sail in space", but are not for the feint of heart.

Your fine dont worry about what books you place in here, we are just recommending a whole lot of sci-fi books for this guy.

Oh man, if you want a good sci-fi book, the best place to start is one of the frist science fiction books ever written, Dune by Frank Herbert. It's the inspiration for nearly every science fiction piece today, including Star Wars.

First Science Fiction books were by Jules Verne and H. G. Wells.

Your best bet is to find a half price book store (used books), and/or visit your library to see what strikes a chord with you.

What I like, you may not.

I dont know if you are trying to link those books to other sites, right now they dont work.

I would recommend (if you can find them) E.E. Doc Smiths "Lensman" - it's very much space opera, but it is the first good space opera, and all other good space opera goes back to it in some way - {G}.

I will second Lois Bujold's Barrayar series - but be warned, they're addictive, but fun.

If you are a Star Trek fan, I would highly recommend anything by Diane Duane or John Ford - two authors that were good writers before Star Trek and managed to translate that skill into the Star Trek Universe - I particularly recommend "My Enemy, My Ally" by Diane Duane and "The Final Reflection" by Ford - *the* definitive books on the Romulans and Klingons respectively. Also, just because, Ford wrote "How much for just the Planet" - a Star Trek Comedy. And it's GOOD!

By the same token if you like Star Wars, you should read Timothy Zahn's trilogy, effectively episodes VII, VIII and IX, Heir to the Empire, Dark Force Rising, and The Last Command.

Jonnan

Most Sci-Fi Historians consider Mary Shelly's "Frankenstien" as the first SF novel.