Science-fiction
This is one of the science-fictionyest of science-fiction novels. Clarke is often seen as one of the most important sci-fi authors, and 2001 has many of the hallmarks of classic mid-20th century sci-fi. There are computer brains, there are aliens, and there are incessant, endless, joyfully bland descriptions of technical details, how weightlessness works, and how Saturn's rings were formed.
At the same time as it's dead center science fiction, though, this book is also a New Age tract of sorts—a vision of benevolent godlike aliens helping humans achieve their cosmic potential. The future in 2001 isn't just a genre; it's also a religion—kind of like Scientology.