There have been hundreds, if not thousands, of books written about the Beatles, individually and collectively: biographies, annotated discographies, musical criticism, and diary-style tomes that cover their every move every day of their seven-year reign over the pop music world. I have read probably 50 of these books, and I still own 27 of them (yes, this pack rat just counted them). Of that number, there are a handful that I consider essential. For their life stories, there's the 2004 Bob Spitz biography (which supersedes the much earlier, and very good but sanitized, Hunter Davies book). For reference, there's Neville Stannard's The Long and Winding Road: A History of the Beatles on Record and Mark Lewisohn's Beatles Recording Sessions (an exhaustive log of every session ever). The best book on their songs (interpretation, influences, etc.) is Tell Me Why by Tim Riley.
Until now, my favorite book about their career and their music in general was The Beatles Forever by Nicholas Schaffner. Though that is still a wonderful book (and lamentably out of print), I've found an even better one: Can't Buy Me Love: The Beatles, Britain, and America by Jonathan Gould. Though the book contains some general biographical information, it mostly focuses on the music and how it both influenced and was influenced by the larger culture. Without dissing anyone unduly or playing favorites (honestly, I can't tell if he prefers Lennon or McCartney, and no Beatle fan worth his or her salt is truly neutral), Gould discusses the songs, the recording processes, the performances, and the critical reception of the music.
Of course, much of the info here has been reported elsewhere, but this is the first time I've come away from a book about the Beatles with a strong overall sense of how the hell they did what they did: record twelve incredible albums over seven years and change the world. Gould makes their chronology crystal clear, especially the areas of cultural overlap: for instance, in 1967, as Sgt. Pepper was soaking into the culture, Brian Epstein died, leaving the Beatles to begin the aimless floundering that ultimately hastened the end of their collaboration: making the ill-considered Magical Mystery Tour movie, going to India for spiritual wisdom, starting the business disaster that was Apple Corps. Gould doesn't go overboard in assigning praise or blame to anyone, but it does seem clear that their decline as a group of people working together (if not necessarily as musicians) dates from the loss of Epstein as their manager; even though by mid-'67, he was mostly just staying out of their way, he was still a grounding force in their business lives.
I love reading Gould on the music. He spends a good twenty pages talking about the music on Sgt. Pepper, and then goes on to discuss the reception of the album by critics, other musicians, and the general public. He does this with each album and most of the singles and always has some new insight or tidbit; for example, that "Long Long Long" on the White Album is essentially Bob Dylan's album side-long "Sad-Eyed Lady of the Lowlands" condensed to under four minutes. He spends three paragraphs on "Norwegian Wood" and more or less pooh-poohs the general wisdom that the song climaxes with the singer setting the apartment on fire (a reading I never really believed).
Despite the book's subtitle, Gould rarely separates England from America in his discussions of cultural reception, and in fact, the sections on politics and other current events of the day are the weakest parts of the book. Luckily, he always returns quickly to the Beatles and their music. While I don't agree with all of his critical judgments (he thinks a lot more of "Yellow Submarine"--the song, not the movie--than I do), I find his writing and his insights always interesting. This is not a new book, having been published in hardcover in 2007, but I just got around to it and I'm glad I didn't let it sit on the "unread" shelf any longer than I did.