Try Eva Cassidy "The Best of Eva Cassidy" 2 record set of all or almost all covered songs is the best for me. Her voice is angelic and spot on pitch wise.... almost chilling. Just beautiful. Hopefully you won't be disappointed.
Your vote for greatest (covers) album
Mine is Annie Lennox "Nostalgia". Not only is she one of the greatest female voices ever, she knows how to make a song her own.