From the Introduction:

This work on Dzogchen by Tsele Natsok Rangdrol provides instructions that are a complete path enabling a practitioner to attain perfect enlightenment within a single lifetime - the unified level of Vajradhara, also known as the royal throne of Samantabhadra. You, the followers of such teaching, pay careful attention to his advice. Short and concise, profound and encompassing, you should study it with great interest. ...

Out of great kindness to destined and worthy practitioners, Tsele Natsok Rangdrol extracted the essence of all the Dzogchen tantras and presented it in a most comprehensive and complete form. ...

The most effective style of teaching for a practitioner in this dark age is not a lengthy scholarly explanation but a direct 'guidance manual' ... a short, comprehensive teaching.

The Dzogchen tantras themselves were written down in a style which shrouds and conceals the meaning so that only a master extremely well-versed in oral instructions and treatises would be able to clarify the tantric statements. A guidance manual, on the other hand, is written down using oral instructions so as to be lucid and simple. ...

Trekcho and thogal are the two main topics in this book.

-- Tulku Urgyen Rinpoche