There are 2 books by John J. O'Callaghan on BookOrb. A strong starting point is How to sell your house without an estate agent (1993). The bibliography below is in publication order, with series grouped in reading order.
Standalone books
Frequently asked questions
How many books has John J. O'Callaghan written?
BookOrb lists 2 books by John J. O'Callaghan.
Where should I start with John J. O'Callaghan?
A good starting point is How to sell your house without an estate agent (1993).
What is the John J. O'Callaghan books in order list?
In publication order: 1. A bit of the blarney (1992), 2. How to sell your house without an estate agent (1993).