You probably can't make any changes to the epub book if they are protected with DRM. If you have non-DRM protected books, the easiset way is to manage your digital library using Calibre, which allows you to download and or edit metadata, including the cover. When you click on "download metadata" it will present you with basically all of the covers for that book which can be found online, and after you select one, it replaces the old cover with that:
This is the best ebook system imaginable.
You're right on one score: ADE isn't intended to edit ebooks, so there are
no edit functions built into it.
The structure of the .epub file doesn't allow editing either. The purpose
of establishing the file type is to keep the integrity of the epublication,
and to establish methods for copyright management. You get what you get -
no changes are permitted. So, I'm sorry that you don't like the title
pages you see - but you're stuck with them.
I just changed the cover of my .epub using calibre, but not through the metadata section. Once you right click on a book, there is an option to tweak the book. You just download the picture you want and replace the cover.jpeg file (meaning you rename the image file you have downloaded and copy it over the old one). Then you just rebuild the book and drag it into ADE and you should see your new cover.
I hope this helps?
As mentioned above, for non-DRM books there isn't much point in using ADE at all, just use Calibre.
However, if you like to keep all your books under a single library I guess ADE is the only practical way.
I was able to do this by using Calibre to edit the metadata and choose a cover for the book that I liked. (I won't explain how to do this because it is very simple.)
The steps involved are rather complicated and seem to me a bit hard to explain, but I will try. In simple terms, ADE stores the cover images for it's library books in a folder called Thumbnails or in a sub-folder of Thumbnails called External. To find this, I went to >My Digital Editions and found > Thumbnails. What you need to do is make a copy of an image that you want to really use for the book cover and then TRICK the ADE software into using your new image instead the old on, by RENAMING the image you want as the name that ADE is already using for the old one. When you try to rename the nice new image with the same name as the old crappy one, Windows will say something like "that image already exists do you want to replace it" and you of course, click yes. Then VOILA the new image is immediately found by ADE.
Here are a few more involved steps saying the same thing:
When in Calibre, I copied the cover that I wanted to add to the book.
Then I right clicked on the image of the cover and chose 'add another application to open'. Then I went and found the software called 'Paint'. (It is well-hidden, but here is the path of folders and subfolders on my computer: C>ProgramData>Microsoft>Windows>StartMenu>Programs>WindowsAccessories It was in the folder called WindowsAccessories
Open the image in Paint, then click on 'file' and chose 'save as'. Next you have to figure out exactly what ADE was calling the crappy image because the new image has to have that exact name. So...
In the folder Thumbnails, or a subfolder in thumbnails, find the current cover that you want to replace. Right click it and select the option "rename". Here is an important key: DO NOT RENAME it. Simply highlight the whole name, all of it, and right click to COPY the full name. Next back in the PAINT program, when you are at the 'save as' step the image you are going to have to navigate into the Thumbnails folder (or external subfolder) and right click and paste in the copied name. This will get you a message like "this file exists do you want to replace it". You click yes or ok and that's it, you're done (If you DON'T get that message, then you haven't navigated to the correct spot.)
GOOD LUCK! Reply if this works for you. Thanks