Read it in French merely for my curiosity in French slang. To be honest, it wasn't the most pleasant read, considering the fact that I DO NOT share the author's opinion at all.
The protagonist is a selfish young dude who is absolutely sure about the fact (that he has made up) that love lasts for 3 years and then it disappers. He was certain about it that even made a kind of research, basing on his personal observations. The poor lover kept telling on every corner that feelings are only strong during firts three year, later they vanish all of a sudden, partners start irritating each other and fall in love with other people. He says that it is high time to separate since these relations cause nothing but anger, sadness and frustrations.
Following his golden rule he left behind two women who loved him dearly. In the end he started realizing his alientation but it didn't make him change his principles