She also says: How many sizes is it going to be viewed at? How small will it be on, say, an iPhone?
It's a nice cover, David. Do ebook covers serve the same purpose as (real books? meatbooks? what the heck do I call them?) printed book covers? Does it need to stand out in a crowd? Pique your interest?
These are all great questions because they reflect the revolution going on in media, with the rise of the phones and tablets (the fifth and fourth screens, respectively, in the life of the modern consumer). If paper books are truly going away and ebooks springing up to replace them, then what of the cover? Is the ebook cover the same or is it different from the paper book cover? (I don't know what else to call them either--traditional books, hard copy books, eventually POD books.)
It seems to me that all commercial covers, whether traditional or digital, must stand out on the crowded rack. Their purpose is mainly to sell the book. The method they employ is usually to be somehow evocative of the subject of the book while piquing the reader's interest. In this the digital book cover is no different than the traditional one, except the crowd it needs to outshine is digital. That is, the ebooks I'm doing will have no POD incarnation and will only be sold online. The online racks belong to Amazon, B&N, and others, and they display covers in sizes ranging from about 60 pixels to about 200 pixels in width, depending where on the site they are displayed. A 60-px cover is really tiny. Here's an early attempt at the cover for My Morning Glory at 60 px. You generally can't read any of the text at this size, not even the title. Objects are hard to distinguish. You may have only a shape and a color. But if you've already looked at the cover in a larger size, then this one acts like a little icon or trademark (a glyph).
Here's an intermediate size that appears on some Amazon pages. (I'm basing these on the Amazon site. Other sites have own sizes. And I have no idea how they appear on a tablet or smart phone.)It's 100 px wide, and at this size you should be able to read something, probably the title, maybe the author name. Object should be discernible.
And finally the size on an individual book's main page. As far as the buying experience goes, this 200 px size cover is the largest that will appear. Sometimes, you can click on a cover and see a larger size, or you can click on "Inside this Book" and see a larger version of the cover, but I would guess that most people don't. So this size has to do all the work.
You should be able to identify objects portrayed and read the title, author's name, and maybe the pitch line (subhead). IMO, there is no place for sub-sub heads.
That's on the sales side. On the reader's side, e-readers also display the cover at about the size of a paperback book. The older Kindles displayed in B&W, but the iPad and Nook are color, and now with the introduction of the Kindle Fire, it seems to me that color will rule on the cover as well as inside the book. The insides of print books have only been shy of color in the past because of the cost of extra print runs that color entailed. But e-color is free, and I believe that ebook designers will embrace it.
More discussion later.