My favorite author, and the one who got me interseted in writing, is Michael Crichton. You've probably seen one of the movie versions of his books (most of them were made into movies). He comes off as an expert on whatever the book happens to be about, and actually did complete medical school so in the case of his novel "A Case of Need" he actually is an expert. I would suggest any of his books, with special mention for Prey, Sphere, Jurassic Park, and Rising Sun.
I mention him, though, for one of his nonfictions, a book called "Travels." It details his love of travelling, telling of places he's been and acting as a sort of autobiography. The book goes beyond just talking about roaming the world, though. He is incredibly honest in this book, which is really about his travels through life in general. Toward the end, his travels become more metaphysical, which is something I did not expect. Through reading him I've always found him to be very scientificly minded, so it was surprising to see him talking about going to psychics and visiting a guru and things of that nature. Of course he was very scientific in his approach to it all, but also very open minded. I really learned a lot by reading this book, and I would recommend it to anyone, especially if you're having a hard time understanding life and deciding where you want to go with it.
On a different note, I must also recomend John Ajvide Lindqvist's "Let the Right one In." I loved this book from start to finish. Also, if you're an aspiring writer, you'll be quite envious of his ability to cut the fat out of his writing and get to the point. It is very well done and certainly not your typical vampire story. He has a few more out, but I still have yet to get to them.