Let me preface this by stating that of course this is an important book, and a translator's job is never easy.
That said, this book benefits from having the original Tibetan available, but suffers from a overly wordy phenomenologically influenced style of translation. Frankly, I have to read the Tibetan to understand what the translator is trying to convey in English
In general, a problem endemic with translations of Dzogchen texts is that the translators often unncessarily make what is relatively straight forward language in Tibetan a conceptual mess in English in their attempt to convey the meaning of Dzogchen into English.
This is a text usually reserved for those with years of personal guidance under a master, who would then explain the basically esoteric statements and explanations. However, those who do have some experience in Tantric Buddhism, especially Dzogchen, will likely benefit from studying this. As Chagdud Tulku explains at the start of the book, this text should be regarded as a holy object of veneration, and even to keep this on one's altar until transmission is received will bring blessings. The text is a compilation of visionary experiences had by Dudjom Lingpa, a famous lama-yogi of the 19th century. His next reincarnation, Jigdral Yeshe Dorje (Dudjom Rinpoche) edited them into the present format, and created a helpful outline of topics, appended to the translation.