Many classical books are romantical. Shut up.
Most of the sci-fi I have is just because of the connections they have with other things. I got Halo and Starcraft because of the games, Jurassic Park because I loved the movies, Harry Potter because I loved it as a kid, and Star Wars because I like the movies. But I don't think the Starcraft and Star Wars ones could stand on their own, the Starcraft ones are fun but the writing is very basic and generally unimpressive, and the Star Wars ones are just like a copy-and-paste of the movies.
Mario Puzo (the guy who wrote the book that the movie The Godfather was based on) is really good. I have the whole Godfather Trilogy (though he only wrote the first one) and all his other mafia based books (The Sicilian, Omerta, The Last Don).
As for thrillers, I'm just getting into military thrillers by Tom Clancy. I only have one of his books so far though, The Hunt for Red October.
[Edited by SuperSkyline89, 8/4/2010 3:01:59 PM]
[Edited by ArchDuke, 8/4/2010 4:09:57 PM]