Eli Bendersky's website (read in Spanish)
This work is probably one of the most famous and highly regarded science fiction novels in history. It describes the encounter of humanity with an ancient alien race, beginning millions of years ago, when humans were just emerging as a distinct sub-group of apes in Africa, and through early 2000s where the first complete encounter occurs.
Although it was written in 1968, the books doesn't feel "old" - its fiction is based on some solid physical principles, and all in all is well researched and presented. As usual in books from that period, too few focus is given to computers, networks and related technologies, although HAL 9000 - the ship's main computer, became probably one of the most familiar "computer characters" in literature. Also, the author was overly optimistic about human progress in space - partial colonization of the moon and cryogenically assisted states of human existence that allow long-range travel by the end of the 20th century are, alas, far from being reality (we do have Twitter and iPhones now, though).
The aliens Clarke presents are also not your usual "N-leg M-head" types that breathe oxygen and speak English with an American accent. Rather, being an intelligent race for millions of years (and perhaps more), they've eventually coalesced with their computers and finally their "minds" merged into the fabric of space-time.
It's a nice book, short, entertaining and easy to read. Recommended.