On the Nature of Things (De Rerum Natura) holds a unique place in the Western literary canon. It is a passionate epic romantic poem attempting to explain the underlying workings of the whole universe.
Lucretius was writing this masterpiece in Latin a few decades BC. It is built on the proto-naturalistic scientific philosophy of Epicurus. This work is considered by many to be the best presentation anywhere of the philosophical thought of Epicurus.
They placed a lot of emphasis on denying the existence of gods or an afterlife. In the single most important point of their thought as far as its influence on me personally, Lucretius made a big point that essentially fear of hell, of being punished in some afterlife, is the biggest source of unnecessary emotional trauma for our species. Contrary to common belief, religion is really mostly NOT in fact a source of comfort, but of horrible and unnecessary trauma.
Let us take this moment to correct a basic misunderstanding about Epicurus. The word "epicurean" now usually gets used as an adjective to indicate hedonism. Epicurus or Lucretius were atheists, and thus believed in taking your pleasures in this life and body. However, they would not have advocated wild hedonism, with likely pain consequences that would outweigh the trivial passing moment of fun. In other words, the Epicurean ideal would not be drunken debauchery, but a nice picnic by the lake- perhaps leading to enjoying a good book under a shade tree while dipping your feet in the cool water. Mmm.
Lucretius attempted to explain the whole universe in rational, empirical scientific terms. Atoms and void exist, and you go from there. One particularly interesting theory here is the "swerve of the atom." This molecular theory of spontaneous random action at the molecular level gets carried forward to eventually explain human free will.
It's beautiful poetry, and a nice view of the emerging idea of scientific empiricism. It's a wonder even simply to appreciate the scope of the author's ambition.