One of Isaac Asimov’s SF masterpieces, this stand-alone novel is a monument of the flowering of SF in the 20th century. It is widely regarded as Asimov’s single best SF novel and one every SF fan should read.

Andrew Harlan is an Eternal, a member of the elite of the future. One of the few who live in Eternity, a location outside of place and time, Harlan’s job is to create carefully controlled and enacted Reality Changes. These Changes are small, exactingly calculated shifts in the course of history made for the benefit of humankind. Though each Change has been made for the greater good, there are always costs.

During one of his assignments, Harlan meets and falls in love with Noÿs Lambent, a woman who lives in real time and space. Then Harlan learns that Noÿs will cease to exist after the next change, and risks everything to sneak her into Eternity.

Unfortunately, they are caught. Harlan’s punishment? His next assignment: kill the woman he loves before the paradox they have created results in the destruction of Eternity.

Isaac Asimov was a Russian-born, American author, a professor of biochemistry, and a highly successful writer, best known for his works of science fiction and for his popular science books.

Professor Asimov is generally considered the most prolific writer of all time, having written or edited more than 500 books and an estimated 90,000 letters and postcards. He has works published in nine of the ten major categories of the Dewey Decimal System (lacking only an entry in the 100s category of Philosophy).

Asimov is widely considered a master of the science-fiction genre and, along with Robert A. Heinlein and Arthur C. Clarke, was considered one of the "Big Three" science-fiction writers during his lifetime. Asimov's most famous work is the Foundation Series; his other major series are the Galactic Empire series and the Robot series, both of which he later tied into the same fictional universe as the Foundation Series to create a unified "future history" for his stories much like those pioneered by Robert A. Heinlein and previously produced by Cordwainer Smith and Poul Anderson. He penned numerous short stories, among them "Nightfall", which in 1964 was voted by the Science Fiction Writers of America the best short science fiction story of all time, a title many still honor. He also wrote mysteries and fantasy, as well as a great amount of nonfiction. Asimov wrote the Lucky Starr series of juvenile science-fiction novels using the pen name Paul French.

Most of Asimov's popularized science books explain scientific concepts in a historical way, going as far back as possible to a time when the science in question was at its simplest stage. He often provides nationalities, birth dates, and death dates for the scientists he mentions, as well as etymologies and pronunciation guides for technical terms. Examples include his Guide to Science, the three volume set Understanding Physics, and Asimov's Chronology of Science and Discovery.

Asimov was a long-time member and Vice President of Mensa International, albeit reluctantly; he described some members of that organization as "brain-proud and aggressive about their IQs" He took more joy in being president of the American Humanist Association. The asteroid 5020 Asimov, the magazine Asimov's Science Fiction, a Brooklyn, NY elementary school, and two different Isaac Asimov Awards are named in his honor.