What do the five factors actually say, and what do they not say?
What it argues
The IPIP items are public domain and measure the Big Five with facet-level resolution. They are the non-proprietary alternative to commercial personality tests. The five factors are descriptive summaries of self-report, stable enough to be useful and not a theory of who you are.
The probe
Take a 120-item IPIP-NEO, then have one person who knows you well take the observer version. Compare; the gaps are the interesting data.
The source
A Broad-Bandwidth, Public-Domain Personality Inventory, in Personality Psychology in Europe 7 — Lewis Goldberg, 1999. The link goes to the text or to a catalogue record for it, not to a summary. This one is a catalogue record: the entry gives you the question and the probe, not the argument in the author's words.