This book was written to impress upon its readers many truths about Purgatory -- first, that it exists; second, that the souls detained there suffer long and excruciating pains, and that they desperately need our prayers and sacrifices; and that we ourselves should strive mightily to avoid Purgatory.
An excellent exercise for the month of November, this book is laid out in 30 short chapters with a prayer for each day. It's a fantastic project to offer as a grace for a deceased loved one.
Confirms in the reader's heart a healthy and holy respect for the sufferings endured by the Holy Souls, such that he will always remember them in his prayers. Imprimateur