I almost tore my hair out as I bought this book to read books from my library imagine my frustration finding that I had to use adobe and that it is not supported on the PRS-T1 (this from Sony Support).
you will find that you cant drag and drop from adobe to your reader as its not recognised
First download the book with Digital Editions (its the only software the library uses).
Once you have it go to the adobe digital editions book find item options its an arrow on the book you have gotten scroll to item info click it,
you then get the path of where the book is stored on your computer.
Mine is: C:\Users\Alun\Documents\My Digital Editions. in the last location My Digitall Editions is the book I downloaded to the computer.
Connect your reader and Load up Reader for PC and you will find you can then drag and drop the file from the computer location onto pc reader, sync the reader and you will download the book onto the reader.
Switch the reader off and then back on again, you will then be able to read the book as normal.
