Prayers are always useful. As God deals in specifics and not generalities, it is helpful to have specific prayers for specific issues. This is an official prayer book by the International commission on English in the Liturgy, so you know that prayers are approved by the Church.
The book is very small, physically, and the prayers are very big, spiritually. Nonetheless, it would be helpful if there were more prayers in the book (for example, among my personal favorites against evil are the long prayer to St. Michael the Archangel, or the Lorica of St. Patrick. The translation of the word "Lorica" demonstrates that its full purpose is to be a protection against evil.
It would also be helpful if any explanation were supplied for the identification of why these particular prayers were chosen and how they are useful in a Christian's life.
The devil is alive and well, and battling fiercely for our souls and trying to destroy our peace in this world. It is always good to be armed against him.
May these prayers bring peace, comfort and strength to all who need it, and to all who pray these prayers.