Exactly which stage did it fail?
Did the Sony show up ok in ADE?
Were you able to copy the book to the Sony?
Was it just reading it on the Sony that failed?
Have you got any 'pure' Adobe DRM books, and do those work ok?
I don't think this is the reason, but could be associated.
There is a bug in ADE2.0 that means some readers work fine with most books, but fail on Overdrive library books. This applies to many Sony ereaders.
With my Sony (PRS-350) plugged in, I can't even read library books on ADE. Unplug the Sony and I can.
Maybe (100% guesswork clutching at straws) the same applies to some other book sources, including "Readbook"
The solution for me with Overdrive books is to use ADE1.7.2 instead of ADE2.0.
I'm afraid it probably won't help in your case as things fail on the Sony even used in conjuction with Sony Reader, but could be worth a try.
There are lots of bugs in ADE2.0 (and 2.0.1). Try replacing ADE2.0 with the older but more reliable v1.7.2.
(You can have them both installed at once if you like.)
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
Some people have found ADE trying to upgrade automatically.
It appears (not 100% sure) that if you install ADE2.0 as a new install (not as an upgrade) that your 1.7.2 will continue to run.
Probably best to say no if 2.0.x installation asks if you want to migrate your library.
I have the book on the reader but the cover doesn't appear and when I open it, I receive a error as if I don't have the right to read it. I will try ADE 1.7... To be continue...
nope ADE 1.7 is no better...
I am afraid I am out of ideas; except maybe you could contact Readbook and see if they can help.
Looking at their website (assuming http://www.readbooks.net/ebooks-solutions/ is the right firm) they do seem to have a rather unusual ecosystem,
and it doesn't mention eReader devices, only PC/Mac, tablets and phones.
Looks more as if it is for the convenience of publishers than of consumers.