The Bigger Bang Theory aka The Struggle of the Ages - can be categorized as satirical/romantic/erotic fiction, with the elements of non-fiction.
Without a doubt, sex is the most complicated and nuanced part of our existence. The ways that men and women and people of all genders put certain importance, mystify, demystify, or imbue it with more or less meaning than necessary. This book is meant to humorously, but also thoughtfully examine the absurdities about how we struggle with it so.
The Bigger Bang Theory is an episodic novel split into 3 parts - Past, Present, and Future. The past includes quasi-historical tales of Caligula and the famous lothario Edward VII as well as more fanciful tales about the first creatures to actually have sex and the discovery/creation of the dildo. The present is a more contemporary look at more modern issues like one-night stands, the role of sex after marriage, and quirky fetishes like fecal play and compensated dating.
Finally, the future moves into SF-like territory with stories about humans and robot lovers, and Handmaid’s Tale-like control of sexual norms. All 3 sections feature historical interludes with some facts connected to each era.
The overall goal in tackling just a wide and tricky topic is to make a fun collection of 50/50 fact-fiction equally as fun to read for pleasure or thoughtful discussion.