For Episode #79 (to be recorded in late June and released in July), we'll be reading Eva Brann's The Logos of Heraclitus and interviewing her about it. She was a colleague of Dylan's at St. John's, and her book exhibits that love of etymology that has come up recently on PEL whenever Heidegger is mentioned, for which St. John's is notorious. This is pretty much what you have to do to talk about Heraclitus, as there are no surviving full texts by the guy. He's just quoted by other ancient writers. You can view all of his fragments here along with where they were quoted, but Eva really goes all out to weave a narrative out of this, bringing in Pythagoras and others whose work she thinks Heraclitus was responding to. The "logos" is about meaning, about patterns: she sees Heraclitus as the first real philosopher of science, who noted that nature performs according to regularities and asked about the relation between that lawlike behavior and the regularities themselves.
He seems to come down on something like Spinoza's view that the lawgiving force is immanent in the matter itself, that everything is in some sense all the same stuff, but that this stuff (which he sometimes calls fire) transmutes according to its internal laws (something like the law of conservation of matter) into the other elements in fixed ratios. The "ratio" part comes from Pythagoras, and is the basis of "rationality:" consistent mathematical relations displays the underlying order of the universe. So there's more to Heraclitus than "the world is a constant flux" in contrast to Parmenides who says "the world is fundamentally unified, static Being."
It's not too late to join the Not School group that I'm running on this. The book is available as an e-book (Kindle, which you can view right on a PC or mac without owning Kindle) as well as in paper (it's cute little pocket book), and though I need to be done with it by 6/20 to record this episode, I plan on running the discussion into July to allow people to take the time they need to get through as much as they want to of it.