The End of Eternity

Andrew Harlan is a 'Eternal', effectively a time traveling policeman. When history takes a bad turn the Eternals work out when the best intervention would be to prevent it. Harlan was one of those who go back in time and effect a minor change to avert disaster.

He's a totally unlikable character, but the book is filled with Asimov's cardboard cutout characters who are all totally without charisma. The plot and plot development are the thing here. Couple that with some cool tech, considering the book was written in the 1950s, and an increasing element of philosophizing about time travel, and it gets its stars.

The alternate time zone of the Eternals is filled with men only. Harlan meets a woman, the only one in the whole book, they make love, he is infatuated, he moves to get her out of her time zone and into his world. Things don't go as planned. The middle of the book is taken up with 'everything that can go wrong does go wrong' and their whole existence is threatened. With his supervisor they cobble together a plan to save everything. There is a longish episodic crisis that issues in a final showdown as Harlan is forced into a drastic decision

The book has all the 1950s expectations that men run the world, women get in the way if they venture into the man's world, and their only purpose is for men to get laid. Male interactions are purely functional and the characters here spend more time being suspicious of each other than working together. The only person with character is the sole female, Noÿs.