Complex sentence: There is a "Best of the boxset" compilation (10 track sampler) that is very rare but available, it features the 10 best tracks from all the cds of the boxset on one single cd.
Split into simpler sentences: There is a "Best of the Boxset" compilation (a 10 track sampler) that is very rare but available. It features the 10 best tracks from all the CDs of the boxset on one single CD.