This title was the first edition of Burke's popular Landed Gentry series which dealt exclusively with Ireland. As a consequence it has great deal more detail about the Irish families included.
While these families are all labelled 'landed gentry', the group is much larger than the traditional landlords, including those aspiring to this status from the professional, business and merchant classes.
While this still represents a fairly narrow group, the family histories are very extensive, including widely diverging collateral lines, junior branches and in-laws. These related families are quite likely to have come from the general farming and artisan community.
These genealogies were mostly compiled by the Irish Chief Herald of the time (titled the 'Ulster King of Arms') and are generally considered to be fairly reliable