Source of Life is a massive achievement in the fields of Himalayan ethnography and Tibetan studies. It is at once a focused regional ethnography, carried out largely between 2009 and 2014, of a seemingly idiosyncratic and vanishing festival tradition in eastern Bhutan and neighbouring Arunachal Pradesh, and a historical and comparative study that ranges the extended eastern Himalayas, with some notable turns northwards to the Naxi and Qiang peoples. This magisterial book belongs alongside Michael Oppitz's similarly massive and likewise beautifully illustrated work of transregional ethnography, Morphologie der Schamanentrommel (Zürich, 2013).

The festivals at the heart of this book go by various names including Pla, Lha, Pcha, Cha, Ha, Lhabon, Kharphu, Roop, and Yaklha. They are all concerned with “ancestor propitiation for revitalization of descent groups”, which largely means securing fertility for humans and livestock (NB: not crops). Festival participants propitiate the srid pa'i lha progenitor gods in the form of one to three apical ancestors, notably 'O lde gung rgyal and Gurzhe, who are invited to descend from the “sky world” to bestow fertility. These two particular gods also represent two strata of cult participants: those descended from Shar Dung migrants who fled Sakya forces from 1352–54, and the “Mon clans” who were part of an earlier migration of Qiang peoples from the north-east, respectively.

These particular “rites for mundane goals”, Huber argues, have persisted outside of the concerns of the Buddhist and G.yung drung Bon salvation religions due to their focus on fertility and their emphasis on a multiple and divisible vitality principle, often called pla. Besides clearly distinguishing these mundane rites from other phenomena identified as Bon, Huber also classifies the srid pa'i lha cult as “non-religious” for its having no soteriology, being kinship based, and being unconcerned with monopolizing sponsorship (pp. 13–16). Huber refers to the central ritual performers as “bon shamans”, who are hereditary, male, do not undergo trance or ecstasy (pp. 163 ff.), or any initiatory sickness, and who participate in a trans-regional “Himalayan shamanic tradition-complex”.

The book is organized into five parts, porously divided between a focused study of the cult in parts I–IV and a historical and comparative analysis in part V. Part I (pp. 11–41) gives an overview of the srid pa'i lha cult. Part II (pp. 43–159) offers a detailed thematic survey of the cult's cosmology and mythology. Among other topics, part II describes various vital forces such as tshe, g.yang, and phya, and how these can apply to one or another gender. It also details the stratification of the “sky world” where the gods and ancestors dwell, and through which they must descend, escorted by bon shamans or their auxiliaries on their verbal ritual journeys. The gods themselves are “ancestor-protectors” and Huber describes the most prominent of them, 'O lde gung rgyal, as “the divinization of the life force and its multiplication” (p. 84). Huber also provides detailed analyses of the mythologies of initiator figures including Gshen rab mi bo, “the very profound bat” and “Ya-ngal the protector”.

Part III (pp. 161–300) describes the various ritual specialists in the cult and their principal techniques. It goes into greater detail on verbal ritual journeys; auxiliary (NB: not “tutelary”) deities of the bon shamans; the bon shamans’ paraphernalia, particularly their headgear; and the characteristic movements of stamping, jumping, and shaking of the main actors in the festivals.

Part IV (pp. 301–559) provides detailed description and documentation of four srid pa'i lha festivals that took place within the same twelve-month period in 2011. These are split between eastern Bhutan and neighbouring Arunachal Pradesh, and are chosen, respectively, to present an intact, conservative festival; a festival influenced by recent migration and resettlement; a festival that emphasizes clan organization; and a now-defunct festival that incorporated a ransom rite and which was transformed by an enterprising headman into a spectacle for Indian VIP guests. The accounts of these festivals are each preceded by short, potted ethnographies, and they draw on Huber's observation and documentation of six further festivals during the research period as well as his further research within the wider region. The section closes with some reflections on the factors quickening the demise of this festival tradition.

In the second volume, Part V (5–252) traces many features of the srid pa'i lha cult up river valleys and over passes north to Lho brag and Gtam shul in southern Tibet, finding notable parallels in the Rnel dri ‘dul ba, a text excavated from Dga‘ thang 'bum pa in Gtam shul, and from the Ste'u and Sha slungs texts. Further parallels are found in some ritual texts from Dunhuang, notably PT 1060 and PT 1134. Huber also found the Mi'u rigs bzhi lha sel to belong to the cult, and traced striking parallels in the Bshad mdzod yid bzhin nor bu (late 1400s), composed in southern Tibet where it was evidently influenced by the cult.

Part V additionally identifies thoroughgoing parallels to the srid pa'i lha cult in the Qiang, Naxi, and Pumi “paying the vows” festivals (pp. 166–82) which, along with several other material cultural, cosmological, and ritual parallels, led to the proposal of a Qiang – and ultimately even 'A zha and Xianbei – origin for many of these mundane rites (pp. 251–2).

The book includes 13 valuable appendices with further documentation (pp. 253–366), including facsimiles of manuscripts, and also features a highly detailed index (pp. 459–96).

Huber displays remarkable skill, judgement, and fluency attending to: material culture; flora and fauna; oral performance; bodily movements; language; and the philology of local vernacular texts, excavated ritual texts from Central Asia and southern Tibet, and canonical Tibetan and Bhutanese histories. Some of the contentions that arise from Huber's method of favouring microtransmissions against the assumption of pan-Tibetan ritual or cosmological substratum – notably with respect to the mountain cult and the ransom rite – may face staunch opposition. Such a debate is to be welcomed, however, and with this book Huber has clarified new vistas in Tibetan and Himalayan studies, transregional ethnography, and the study of mundane rites.