For most people, I think his online catalog of refactorings and blog articles are sufficient. Though I think the first edition is a good book, I wouldn’t need it if I didn’t do research on refactoring tools.
I've seen a similar, entire book dedicated to database refactoring that had roughly the same pattern. Chapters named akin to "The Change Table Name Refactor" felt kind of bizarre, when what I was hoping would be contained was advice about refactoring large databases in practice (moving data to new service boundaries, etc). Practical advice on building systems to move data and such seems to be just missing
Trivial after the book exists, sure
The catalog misses out most of the interesting discussion
Refactoring helped me start to understand the 'why' and 'when'. Why is design A better than design B? When is it time to tidy up this code? Which choice will be easier to change later? That kind of thing.