Palantir Technologies, a Peter Thiel-backed data analytics company best known for working with government spy agencies, is preparing to trade on public markets for the first time on or around Sep. 23.

Palantir, though secretive, has attracted a lot of buzz through the years. And Thiel has a strong reputation as a co-founder of PayPal and an early investor in both Facebook and Microsoft's LinkedIn. Those investments have paid off handsomely for shareholders.

Should investors buy Palantir? Here's what you need to know before you do.

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