This was (before losing it) simply the best thesuarus I had ever owned, now unfortunately unavailable. I had the most frequent hits and best chances of pinning vague notions than with any other thesaurus. Why? The entries were loose enough to make a fortuitous match more likely than with the more synonym-accurate, and therefore restrictive, versions. A loose association is precisely what makes for a good thesaurus: it allows the groping, fumbling mind (a mind which doesn't yet know what it is looking for) bump into the word or thought, which was only vaguely guessed at, and which, one discovers in the end, to be only very remotely connected to search word/phrase.
An unusual feature of this tome was that the index contains all (ALL!!) the words and phrases in the thesaurus, thus making searches far more productive. A huge advantage. What is more, there are more varieties of different Englishes (British English, American, Canadian and Australian Englishes) represented. And, for those who love words and ideas, it makes for an unbelievably good read: most entries are headed by pithy quotes and sayings associated with the word or concept - you actually get an education as you search.
Most thesauri follow the Aristotelian system of ordering, which I have found doesn't work for me. It is too "accurate" and restrictive. The Platonic is far more suggestive and generative.
However, the book is out of print and, like all good things, appears briefly, proves too good and too innovative for its time, then disappears. As the reviewer below states, the best, it seems, is not for us.