•Why it earns a slot
Why it earns a slot: it is the single surviving source for most of what we know about the Greek philosophers as people, gossip, quips, and death scenes included, not just their systems.
A gossipy Greek compiler strings together the lives, jokes, and death scenes of every philosopher who mattered, from Thales tumbling into a ditch to Epicurus dying in a warm bath.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.