Your shiny new book is launched, people buy it... people read it... and then some of them review it. What do you do? Do you not look at the reviews all? Do you look at the overview/breakdown of how many reviews are 5*, 4*, etc? Do you read every single review, good, bad and indifferent?
I suppose it depends on who you consider the reviews are for. Other readers, certainly. Other readers will look at the title and cover, and then may read the blurb. Most readers I know also look at the reviews (or at least the distribution of stars in the reviews) before buying, if they're buying online (and may well have done this kind of research before going to purchase the book from a bricks and mortar bookstore. I know I do).
Are reviews there for the author?
An author will (hopefully!) have spent a lot of time writing the best book they can, structuring it, developing their characters, choosing their words carefully. They should have had feedback on the book from the editor (assuming they or their publisher employed one) and honed the book and polished it up to the best of their abilities. Is it helpful to know whether people loved/hated their book?
If people loved their book, then that can be a confidence boost and some validation of their hard work. It can reassure them that they have produced something that others have enjoyed reading.
The value of a negative review...? That might depend on why the reader left a negative review. They may not have enjoyed the book - everyone likes different things and this book wasn't for them. That opinion might help another reader, but I'm not sure it helps the author.
If it's because the book was riddled with spelling/grammar/formatting mistakes, or other kinds of errors that should have been corrected (incorrect factual information), then yes, this might be useful to the author, though it should also be fed back to the editors who should have spotted the mistakes before publishing.
If they didn't like the characters or the story, there's not much the author can do about that and for many books, there can be as many people loving the characters as there are disliking them - how does a writer deal with that?
Whatever the reason for a bad review, the author can't change the book that's published. Newer editions might be updated to correct any mistakes, but fundamentally, the book is what it is. The writer may think about what they are currently working on, or the next thing they write, and reflect on the reviews, but should reviews of book A influence the writing of book B?
What do you think? Do you think that authors should read their reviews or not?