As it says in the translator's preface, this book is intended for Heruka practitioners who have received the complete empowerment into the body mandala of Heruka, but it can be read by anyone who has a highest yoga tantra empowerment.
There are certain practices that I never do, however, I have read commentaries on such practices because there are subjects within it that are applicable to other practices. Certain lineages stick more strictly with tradition whereas others are looser or have changed the presentation for modern practitioners. For example, the strictly traditional approach in the Gelug lineage is that in order to practice Heruka body mandala you must first receive the outer empowerment of Heruka 5 deity, followed by the complete empowerment into the body mandala of Master Ghantapa. In the New Kadampa Tradition, Geshe Kelsang Gyatso Rinpoche received direct oral instructions from Trijang Rinpoche regarding the changing of presentation to suit the needs of his own disciples, in which case, the body mandala is given as the principle Heruka initiation, the 5 deity is no longer given, and people who have received the body mandala initiation can practice it.
Anyways, if you've received any HYT empowerment, you can read such commentaries. However, to practice it or receive the real benefits it is essential to first receive the appropriate initiation.