On to the Sanumas is a firsthand account of Don and Barb Borgman's forty-year effort and achievement to place the word of God into the hands of the Sanumas, a tribe of the Yanomami people of Brazil. The edited compilation of personal letters, journal entries, and newsletters is a detailed record of their many years with the tribe and the friendships they established among them. It is a story filled with toil, adversity, trials, and even tragedy, yet also one of joy and evidence of God's faithfulness and love. The book provides great insight into the Sanuma people and their way of life as many experienced change from animism and shamanism to faith in Jesus Christ. It is also a historical record of the first contact expeditions to the Yanomami people by missionaries of Unevangelized Fields Mission in the late 1950s and early 1960s. These are all recorded by Borgman. This is an important work in that it chronicles not only the lifework of this missionary couple and family, but also another chapter of the ongoing expansion of God's kingdom to the ends of the earth. It is a valuable read for both academics and laypersons in the church.