The first Jamgon Kongtrul, Jamgön Kongtrül Lodrö Thayé (འཇམ་མགོན་ཀོང་སྤྲུལ་བློ་གྲོས་མཐའ་ཡས་ 'jam mgon kong sprul blo gros mtha' yas), was one of the preeminent scholars in 19th century Tibet, often referred to as Jamgon Kongtrul the Great. The name Kongtrul is a contraction of Kongpo Bamtang Tulku, of whom he was held to be an incarnation. He also was a tertön, or "revealer of Dharma treasures," and in that capacity was given the name Pema Garwang Chimé Yudrung Lingpa.
He was also a respected physician and diplomat. He is credited as one of the founders of the Rimé (རིས་མེད་ ris-med "unbiased" or non-sectarian) movement of Tibetan Buddhism, and he compiled what is known as the Five Great Treasuries.
The brilliant 19th century rime classic on the fundamentals of sadna practice. Suprisingly readable. Lots of rich, valuable detail on the meaning of visualizations and the psychic mechanics of sadna practice. Recommend it very, very highly for vajrayana students. Anyone else, though, wouldn't be so appropriate.
A teacher of mine translated and introduced this book, Sarah Harding. And my favorite Author other than LT, Kenchen Trangu Rinpoche wrote the commentary. Though some say the translation and the commentary do not go together, I think it's a perfect match, even if a little indirect.