I read a lot of fiction, particularly Science Fiction and Fantasy. I also enjoy History and biographies, and occasionally an interesting book about math or physics.
Below is a list of my favorite and most influential fiction authors.
Terry Brooks. The Shannara books were some of the first Fantasy books I ever read. They were introduced to me by my fifth grade teacher, first from a library of books she kept in her classroom, and then from her personal library when I ran out of classroom copies. I read the entire original trilogy and the Heritage sequels that year, and the stories have stuck with me.
They calibrated, I suppose, my personal sweet spot of the fantasy genre: darker, and more down-to-earth and frank than Tolkien's works (and I'll admit I've never been able to make it through The Lord of the Rings), yet still far more idealistic and optimistic than G.R.R. Martin's 'Low Fantasy' full of horrible people doing horrible things.
Celia S. Friedman. I've enjoyed everything I've read of hers, but especially the Coldfire Trilogy. From the opening scene, through the Sci Fi hints, to the inner struggles of the main characters, the books are all fantastic. They're dark, yet still full of hope that humanity can be more than mere reaction and survival, even if we have to travel through some very nasty places to get where we're going.
Mercedes Lackey's Valdemar books were with me through my adolescence. I still love the diversity of characters, cultures, and even species in them, as well as their abiding optimism. I think she's a master of living, iterative worldbuilding—often expanding the boundaries and adding new complexity in a way that feels natural and seamless.
Connie Willis. I've enjoyed several of her books, but To Say Nothing of the Dog is quite possibly my favorite all-around book. An upbeat, satisfying time travel story is something special, and her presentation of a semi-malleable timeline with multiple extemporal influences is both intuitive and fascinating.
Iain M. Banks' writings contain some of the most coherent and frankly skeptical thoughts regarding 'utopias' I've ever experienced. Starting off tales about one such civilization with Consider Phlebas—a story told from the point of view of a staunch enemy in their first war—is both a brave and fascinating choice. The Culture novels show various views of how a single utopia could work, but his standalone novels also show interesting views of potential intermediate or end states of civilizations.
Verner Vinge. The Zones of Thought universe is incredibly intriguing, doing a fantastic job of making the galaxy seem huge, but crowded, and humanity's place in it very very small.
While much of the thought about artificial intelligences these days is that the first or least-flawed superintelligence will become a dominant and hegemonizing force, Vinge has developed a single example of a framework in which there are mitigating factors. While the Zones are a contrived, extreme construction for this purpose, it's a nice launching point for thinking about how other factors—no FTL, galactic-scale natural disasters, etc.—could make the landscape of intelligences more diverse.
Karl Schroeder's Virga books are strange beasts for me. I'm not a huge fan of steampunk and similar settings, but from the very start it's clear that, while the pervasive setting is such, the overarching universe is much more. So, it was that mystery that drew me in, and I was well-rewarded.
I think the core idea which is laid out as the Virga series progresses is a very important one. Too often we look at creating sentient, sapient machine Minds as just another programming project, something we can architect and engineer into existence, like an office suite or a skyscraper. This is an incredibly cold viewpoint to take about the creation of new life, and it's both valid and terrifying to think of doing so, and then finding ourselves with an intelligent—even superintelligent, 'post-Singulary'—being which has exactly as much ability to relate to us as a copy of Excel.
In Schroeder's world, long after such a creation has occurred, we—baseline humanity—end up more able to relate to e.g. the more evolutionarily generated gestalt that forms when non-sapient (but still very capable) machines attempt to fulfill the needs of oak trees, than to coldly, deliberately created individual sapient machines. At least with trees, we share the commonalities of needing water, food, air, and of having an evolved drive to reproduce and perpetuate.
Really, the idea of a gestalt 'mind' formed around a non-sapient (even non-sentient) being evolving into something we can relate to is a sort of tech-enabled, macroscopic copy of the human mind and its development. The very core of our brain does no thinking at all: the brain stem simply keeps our meat alive. The rest of our minds, our emotions, logic, artistry, language, these are all just 'programs' which we've evolved and kept because they gave us some survival advantage. A Mind without this shared history would be something truly alien.
Laurell K. Hamilton. I miss old Anita Blake. The stories were pure pulp vampire schlock, but written with wit and style, and tightly constructed. As they transitioned more towards the lucrative "let's screw lots of magical beings!" genre, they also transitioned into weaker writing and messier editing. I gave up after Narcissus in Chains. I won't pretend the addition of a love interest with my name didn't influence the decision...that was pretty weird.
And many others... Stephen Baxter, John Scalzi, Charlie Stross, Robert Jordan, Steven Brust, Terry Pratchett, Isaac Asimov, Alastair Reynolds, Jack L. Chalker, Piers Anthony. If you go back far enough a bunch of old Magic: The Gathering and Shadowrun novels by various authors...and hey, even The Hardy Boys and Goosebumps.