Barbara Bonney has a voice that I personally find expressive and ravishingly beautiful. Her technique is flawless, which is one of the reasons why she is so in demand for masterclasses.
She has an intimate understanding of Schubert lieder and, from the point of view of style, I personally cannot fault her. Her singing is expressive but nothing is ever done that undermines the sheer beauty of Schubert's musical line. I have played this recording to friends with no knowledge of classical music and they too have acknowledged the sheer artistry behind the recording.
I do note that others have referred to this as an introduction to Schubert's lieder. Personally, no matter where one starts, I consider it all accessible, although I must confess that many of these pieces are particularly well known (and rightly so).
...and I love this version of "Shepherd on the Rock".