The Time Machine: by H. G. Wells

The Time Machine is the novel that gave us the concept of-and even the word for-a "time machine." While it's not Wells' first story involving time travel, it is the one that most fully fleshes out the concept of a device that can send a person backwards and forwards in time with complete precision. Time machines have since become a staple of the science fiction and fantasy genres, making The Time Machine one of the most deeply influential science fiction novels of the era.