I highly recommend Greg Egan. I don't know if his works are to be considered hard sci-fi, as they are sometimes very speculative. His novel "Quarantine" is about what happens when scientists create a device that lets the user manipulate quantum states and intuitively "choose" the best outcome, however improbable. And from there it just gets even more complicated.
A short-story compilation named "Axiomatic" is also highly recommended. Here is a list of the stories it contains, from Wikipedia:
" * "The Infinite Assassin" -- An illegal recreational drug allows people to travel between parallel universes with disastrous side effects.
* "The Hundred-Light-Year-Diary" -- After the invention of a method for sending messages back in time, history of the future becomes common knowledge, and every person knows their own fate.
* "Eugene" -- A married couple consults a genetic engineer to design their next child.
* "The Caress" -- Police investigate the origin of a half-human, half-cheetah chimera discovered in the basement of a murder victim.
* "Blood Sisters" -- Two identical twin sisters are diagnosed with the same rare, fatal illness.
* "The Safe-Deposit Box" -- A man inhabits the body of a different person every time he wakes up, and has lived this way his entire life.
* "Seeing" -- A shooting victim's brain damage causes a permanent hallucination that he is watching himself from a bird's-eye view.
* "The Moat" -- Sperm taken from a rape victim are found to contain DNA altered to be invisible to genetic testing.
* "The Cutie" -- A man longing to be a father uses recent advances in biotechnology to impregnate himself with a "Cutie", a child with sub-human mental capacities, sub-human legal status, and a lifespan of four years.
* "Into Darkness" -- A giant sphere of unknown origin jumps between random locations on the Earth's surface and restricts the movement of objects trapped inside in bizarre ways.
* "Appropriate Love" -- A woman carries the brain of her severely injured husband inside her uterus for two years so that a new (brainless) body can be cloned to replace his.
* "The Moral Virologist" -- Inspired by the AIDS epidemic, a fundamentalist Christian devotes his life to the creation of virus that will kill those he views as sexually immoral.
* "Unstable Orbits in the Space Of Lies" -- An unexplained event causes everyone on Earth to rapidly become ideologically sympathetic to people physically nearby, creating a world with clear geographic boundaries between religions and philosophies that cause instant conversion for those who travel between regions."
