Consuming many hours of my time lately has been a science fiction series written by Issac Assimov. I picked the books up for a few pounds in second hand bookshop and the thing that convinced me to buy was a preface in one written by Arthur C Clarke. I'd been reading and enjoying a lot of his work and the preface was complimentary of Assimov.
They're fantastic! I've bought some more of his books now (also from the second hand bookshop) and have my eye on a couple of others. Amazon have a system where people can sell second hand books too and I think I may well buy the ones I can't find in the local second hand bookshop.
The Foundation stories cover several centuries from the Fall of an empire that spanned the Galaxy to the rise of it's replacement. All based around a theory that one man in the start of the story had that the actions of groups of people can be accurately predicted (whereas the actions of an individual are more unpredictable). He forecast the fall of the empire, and then put in place things to replace the fallen empire with a new empire as soon as possible, hopefully preventing the loss of knowledge and technology and turning the possible 30,000 year galactic dark ages into a period of just 1,000 years. The story is addictive and quite unpredictable. I've found many stories seem to come to a conclusion to soon and I want them to continue, I think this is one of the first series I've read where that hasn't been an issue. By the way, read them in the order "Foundation", "Foundation and Empire", "Second Foundation".