I really enjoy alternate history stories. These are history where you change one signal event and see what will happen. Probably the best at the game is Harry Turtledove. He wrote a series about World War II where, in the summer of 1942, an invasion fleet comes into orbit around the Earth. The invaders are a lizard people from a desert world whose culture has been stable for hundreds of thousands of years and who had expected to find us stoiill at the stage their scout ship had seen at the time of the First Crusade in 1098. The Lizards have advanced technology, about that of 1995 Earth, so they are not invincible, just a very difficult opponent. It is fascinating to see how the various historical figures play out in this new environment. they are "Worldwar", Vols. 1-4, "Colonization", Vols. 1-3, and Homeward Bound, so far the only one. He also wrote what I consider to be the best "if the South had won the Civil War" book, The Guns of the South, and a hilarious magical mystery, The Case of the Toxic Spell Dump, a wporld where magic works rather than science and an employee of the EPA, the Environmental Perfection Agency wishes that he lived in a clean world of science where he didn't have to deal with the toxic side effects of magic spells.
Eric Flint is cooking along with a great series about a West Virginia coal mining town set down in the middle of the Thirty Years War in Theuringia, Germany, in 1632. The first book is 1632. Flint also collaboated with David Drake in a great series based upon the Byzantine general, Belasarius, but with the twist of having botht eh good guys and the bad guys receiving help from the very, very far future. Also try Flint's Pyramid Scheme. It's one of the funniest books that I have ever read and a very knowledgeable spoof of Greek mythology and of role-playing games as well as some of the classic s-f themes.
S.M. Stirling is another great alternate world author. His Domination is a very grim series of stories about the Draka, South Africans in a world where they were the Tories from our Revoluti0on, the Confederates from our War Between the States, and various losers from other wars who decided that they would NEVER lose again and they don't.
Fred Saberhagen is the author of two very different series. His "Berserker" stories are hard s-f about a race of machines created in a long ago war whose purpose is to wipe out all biological life as ooposed to their mechanical life. Mankind comes up against them in its expansion into the stars and it becomes a war to the knife, either mankind or the berserkers must be exterminated. If this sounds like the "Battlestar Galactica" tv series, it is. They stole the idea from Saberhagen. And a description of a Berserker machine will give you an immediate idea of where George Lucas came up with the idea of the Death Star. The best of these is the short story, "Wings Out of Shadow" which gave birth to a role-playing game and to a computer game, I believe. His other series is about Dracula where Dracula is the Madieval warlord, Vlad Tepes of the family Dracul, Prince of Walachia and terror of the Turks. Saberhagen wrote the shooting script for the film, "Bram Stoker's Dracula" by Francis Ford Coppola that came out a few years ago, so you may have some idea of the sort of character that Saberhagen had created. Dracula is very much the Medieval warlord, with a strong sense of honor and of duty to his friends. This makes up the baseline for most of the stories, where he is protecting the descendents of Mina Harker. The first book in the series is The Dracula Tapes wherein you get to hear Dracula's side of the famous Bram Stoke novel. Van Helsing does not come out looking very good, that much I will tell you. There is one lovely piece where Dracula is trying to gain information from a hireling of an old enemy who is attacking Mina's descendents. He grabs the guy's hand and begins to pull the fellow's fingers off, one by one, until the guy talks. Very Medieval.
I can recommend almost anything by such old masters of s-f as Isaac Asimov, Robert Heinlein (his last writings aren't as good as his earlier stuff), Poul Anderson, Roger Zelazny ("The day I read he died...I cried...in the middle of a bookaisle. The thought of no more of Roger's tales shook me....made me mad and deeply sadden. I have since survived cancer myself.....and reading the man's work helped bring me joy and wonder throughout the process.....I shall forever miss him and all his words.
Lewis), who wrote what I sincerely believe to be the finest short story in the English language, "A Rose for Ecclesiastes". Another delight of Zelazny's many is Roadmarks about a guy who is trying to smuggle M-1 Garands back through time to the 300 Spartans at Thermopylae. You may gather that I like Zelazny and you are right, but no more than the others, not really. Also, try Theodore Sturgeon, H. Beam Piper, Philip K. Dick, Keith Laumer, James H. Schmitz, and E. Bertram Chandler. That should keep you occupied for a while, at least.
I'm open to suggestions of all types. Just no romance novels. 
.....Long time ago. I also liked the way he incorporated some neat surveillance/tracking stuff into the plot. I'll have to look into the Wilson books with Repairman Jack. THX!
