M. D. Healy parcels out advice in helpful bits. For instance, disparity between where an infant is born and where the census records the baby's residence may be attributed to the mother's tendency to return to her own ancestral home to give birth. Naming orders for sons and daughters delineate the maddening tendency (my pedigree attests to this!) of repetition every two or three generations. In the past, the range by horse or bicycle might explain the relative proximity of a courting couple's homes.
Looking into the Constabulary data, as well as parish baptismal records, can replace the lack of census information for many decades in the nineteenth century. Abbreviations of first names (or in parish documents, the Latin forms of them) common in data, it's good to expand searches in archives to account for these--as well as surname variants. The author also reminds us of transcription errors. (I have one clan in my family tree I've found spelled in the records three ways over two generations.)
Healy intersperses, more willy-nilly into the short sections of a few paragraphs, his own north Mayo connections and culture, place-name or local Irish lore, and application for "Citizenship by descent" guidance. (He errs when citing as "1830" the Republic of Ireland's legalization of this status; I also think that it merits mention that such a status cannot be passed on to one's own foreign-born descendants.) You even get a distant cousin's shaggy-dog tale about the Irish genetic descent from the Basques.
All in all, this replicates a genial long chat in a pub with a professional genealogist. However, it's a very, very brief e-book. My Kindle had no table of contents, and while a short reading list is appended, more was needed in the text about "finding your Irish ancestor's birthplace" as to the learning where the locations of "the full compliment" of records might be consulted. Some records are now coming online, but many have or will not. Knowing the difference for those who may have hit that "brick wall" in an initial online search would assist the American audience for this book.
Healy's approach rambles even within these small parameters, but the tips he shares will encourage those who now have the benefit of the Net to do what some of us--not long ago--had to do with waits for the big tomes at Dublin's Public Record Office, the tax records from the Land Valuation archive, or the microfiche lists at Irish county libraries. These, still, may be consulted with benefit, by professional or amateur genealogists. His comments here are parsed out as but a few in total, but they may point you in the right direction