For an FP person, you might want to instead start with skimming, for half an hour, the R5RS or R7RS Scheme paper, for the base language from which Racket grew (don't worry about the first-class continuations unless you want to). Then go to the Racket Guide or Racket Reference table of contents, to look for things that you might be looking for from your past FP experience, like `match` (though it's maybe not used as much as you're familiar with). Then look into some of the strengths of Racket, like syntax extension and `#lang`. (If you want additional treatment of syntax extension and `#lang`, see things like Hendershott's "Fear of Macros", and Butterick's book.) Also skim the large list of add-on packages, to get a sense of what's there. Eventually read through the Guide and Reference at your leisure.

There's an imposing wall of manuals at: https://docs.racket-lang.org/

Racket isn't purely FP, but it can be used that way, even with the base language. There's also at least one lazy `#lang`, and you can make more.