Pleased to see Roget's thesaurus here. It's a fantastic resource without a great digital equivalent. I've found LLMs helpful in a pinch (and it's certainly better than a standard thesaurus), but Roget's is still the book I turn to for tricky word-picking problems.

Roget's Thesaurus is part of Project Gutenberg: https://www.gutenberg.org/ebooks/22

From the preamble of the edition published by PG:

  Note that this version of Thesaurus-1911 has been supplemented with over 
  1,000 words not present in the original 1911 edition, but many modern words 
  are still missing. About 1500 verbs (out of 6500) which can be found in an 
  80,000-word spell-checker are absent from this work. The deficiency of nouns 
  is probably much worse, especially on technical topics. Of 40,000 unique 
  words contained in the original text, 12,000 are not recognized by a 
  spell-checker. Most of these are foreign words (primarily Latin), and many 
  are obsolete.

I've never owned a copy of Roget's, and now I'm curious/tempted to get one, but my go-to digital word picking assistant has always been OneLook Thesaurus: https://www.onelook.com/thesaurus/

Hey, I'm the developer of OneLook. I'm so glad to see it here! The concept clusters on the site are directly inspired by Roget's work. Like the author, I see a thesaurus less as a synonym dictionary and more as what the word literally means, a storehouse of treasure. I'm in the midst of a long-overdue data refresh across OneLook right now, so I'd be curious to hear your feedback once it's done.

I was looking for it after reading the post, but there seem to be so many different versions and edtions. Harper, Penguin. College. The New. The Concise. The International. Some say they’re organized alphabetically. How do I know which one is the kind that the article talks about, if I buy used online and cant look into it?

Are you in the USA? It's because Roget as a title isn't trademarked there so it's accepted as a name for any thesaurus.

If you want the latest edition of the "real" Roget's, it's the one published by Longman.

The one in TFA is Harper and Row, and the later 8th Edition, published by Harper Collins, is also organized the correct way. I think you'll be safe if you can get a Harper version.

That's the one I have. I've had an older version in the past but misplaced it years ago. This one does the trick, but like the article author says: it is a weighty book. (I like that.)

I never knew Roget's was organized like that and I have had several different editions over the years. I'm one of those people who always used it as a compendium of synonyms.