This should be all of the Idolm@ster albums released to date, excluding the drama cds and radio cds.
Audio is tta encoded, with cue sheets. You should extract the cue sheets from the included 7-Zip archive. Artwork scans were included where available.
If you're having trouble with playback, I'd recommend trying Foobar2k on windows, with the tta plugin found here: http://www.csie.ntu.edu.tw/~piaip/foobar2000/