The Birth of Venus is an iconic image and a cliché; but it is also a work of utter mastery. Rather than attempt pure photorealism, Botticelli chooses an almost cartoon-like style of sharp outlines filled in by washes of colour. Today we would call the deliberately crude rendering of the trees, shoreline, and water some form of Rousseauian Primitivism. Botticelli clearly has the skill to work just a realistically as he desires; I conclude that his primitivism is deliberate. Botticelli understands that by simplifying away the level of the smallest and least essential details what is left has all the more visual power. Simplification or no, not only are the outlines gorgeous but the colour washes are divine. Look at how limid and luminous are the colours in Venus' skin. (Yet for all that Botticelli manages to get Venus' left nipple in the wrong place, which suggests along with the sloping shoulders that she was drawn from imagination, not life.)
The story line is simple: we have Modesty attempting to cover the new-born nakedness of Beauty, while the god Zephyr (perhaps with a reconciled Chloris in tow?) attempts to prevent this tragedy from coming to pass.