Like "A Piece of the Action" before it, "The Big Goodbye" is Star Trek doing a completely different genre and coming up gangbusters. Whether or not you hold against it that it's also the source of holodeck-run-amok episodes is up to you.
One of the unlikeliest but most enduring (famously featured in Star Trek: First Contact) features of Picard's character was his fascination with the pulp fiction detective Dixon Hill. On the surface, this is the Dixon Hill episode. It's also the first notable pairing of Picard and Data, who would go on to dominate the Next Generation movies
It's also good fun, and that was extremely rare, both before and after, in this series. Deep Space Nine, which a lot of fans pegged as the darkest Star Trek, had a lot more levity. Aside from visits by Q, Next Generation tended to be pretty sober, taking the lead of Picard, so it's that much more notable that "The Big Goodbye" actually features him in the lead.
Another element worth mentioning is the Federation historian featured in the episode. Although between this and "Space Seed," it may not be the greatest career path in the future.
Sit back and enjoy!
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Memory Alpha summary.