Indeed, this Pius was more in the mold of Pius V (1566-1572), who wound down a council, of Trent, or Tridentum, 1545-1563, and followed through on its edicts and findings with the mass called Tridentine.
This 5th Pius curiously has this in common with his successor-reformer of four centuries later, Paul VI, who followed through on a council he also had not convened with a new mass, “Novus Ordo,” with radically new script and stage directions.
The two masses endure, the first as barely tolerated (by never-Tridentiners among higher clergy and arguably the pope) or lovingly cherished (by traditionalists, or “traddies” as some call themselves) — whereby hangs a dramatic tale.
To these latter this book is mainly aimed, they being a hard core (corps, you might say) of worshipers and increasing numbers of the religiously curious, a curiously growing bunch. (See Western Canada millennials in this 11/30/2018 Crisis Mag piece)
As for the the new mass, it has been offered for much of its life on pretty much a take it-or-leave-it basis, illegal at first — with an endearing exception — and restored in stages by two popes, John Paul II and Benedict XVI. It remains a minority experience, however.
Of which more later . . .