Michiko Kakutani breaks the embargo:

a copy of which was purchased at a New York City store yesterday, though the book is embargoed for release until 12:01 a.m. on Saturday

And writes Rowling a love letter. [Warning: There be spoilers.] Excerpts:

..monumental, spellbinding epic, 10 years in the making, is deeply rooted in traditional literature and Hollywood sagas — from the Greek myths to Dickens and Tolkien to “Star Wars.”
[..]
While Ms. Rowling’s astonishingly limber voice still moves effortlessly between Ron’s adolescent sarcasm and Harry’s growing solemnity, from youthful exuberance to more philosophical gravity..
[..]
This same magpie talent has enabled her to create a narrative that effortlessly mixes up allusions to Homer, Milton, Shakespeare and Kafka, with silly kid jokes about vomit-flavored candies, a narrative that fuses a plethora of genres (from the boarding-school novel to the detective story to the epic quest) into a story that could be Exhibit A in a Joseph Campbell survey of mythic archetypes.

In doing so, J. K. Rowling has created a world as fully detailed as L. Frank Baum’s Oz or J. R. R. Tolkien’s Middle Earth, a world so minutely imagined in terms of its history and rituals and rules that it qualifies as an alternate universe..