Larry Brennan, from Clare Roots Society, has provided an explanation of just what they are...
If you look through the indexes on the left hand column, you will see all the postings by IGP.
PRIMARY VALUATION OF IRELAND CANCELLED BOOKS
updated every 12-18 months to record any changes in the ownership, occupancy
and value of the property between Griffith's Valuation and 1977, when rates
were no longer charged on residential property.
You can trace the occupancy of a specific address from the earliest point
until 1970, unless otherwise requested.
You can get copies of the cancelled books that record any changes to the
ownership, occupancy, size or value of the property.