A friend in the business called the new Masterpieces of Music guides to my attention a couple of months ago, and I have finally taken a look at the first of the guides. It's an electronic book introduction to Beethoven's Symphony No. 3, "Eroica." The text and analysis are by music writer Matthew Rye, and the guide includes Andrew Manze's Harmonia Mundi recording with the Helsingborg Symphony Orchestra. (All of the guides will include Harmonia Mundi recordings, in fact.)
The audience for this type of guide is a listener who can read music and knows a little bit about keys and key relationships, and who wants a detailed walk-through of the symphony. The bulk of the 125 pages of the ebook is taken up with the score, analysis, and various musical examples. The analysis looks fine from a technical standpoint. I would say that if you're going to claim that there is something special and elemental about the key of Eb, you need to say something about the theory behind keys and key relationships before equal temperament took over.
Although the press kit touts "the latest scholarship," there can't be more than about ten to twenty printed pages on the history and reception of the "Eroica," and I could not find any references in the ebook to additional books or articles. To state the obvious, there is a vast literature on this symphony and Beethoven himself. If you want to take a serious look at the literature, start with the New Grove article on Beethoven, or Lewis Lockwood's biography, which must have an extensive bibliography.
I looked at this book in a browser on my desktop machine and didn't try to download the book to my phone or tablet. It looks pretty good (except for those huge and oddly-spaced block quotes and a couple of pages with white print on red - yech), although the sound clips interspersed with the text sometimes overlap the text when you change the size of the browser window. Some additional information is presented as a pop-up window; other information appears in a new tab. The new tabs weren't always obvious, and at one point I found myself wondering where the hell the main text had gone.
I also looked around for a while trying to figure out whether you can play the whole symphony through, rather than just the excerpts, and never did figure it out.
I am not the audience for this kind of book, but you might be. If you try out one of these - and there is a new book for the Bach Mass in B Minor, with the Brahms Piano Concerto No. 1 forthcoming - let me know what you think. For around $8, they're not a bad deal.