If you are looking for professional book reviews, I would probably say Publisher’s Weekly. But the problem with the “big” reviewers is that they give priority to “big house” publications whose publicists can get the books in front of their reviewers. If you are a fan of a writer who is not a “big time” author, or of a category that doesn’t usually get covered in that kid of review (stuff like romance, mystery, horror) you would probably get a better sense of the book to read the reviews on sites like Goodreads, Library Thing or blogs dedicated to that category.
I haven’t liked all of Ishiguro’s books, but he writes beautiful and original prose. I just wonder if the majority of readers are educated to recognize it anymore. I like mystery novels and popular fiction as much as anyone, but The Remains of the Day and Never Let Me Go will live on after people forgot about One of Us Is Lying.