The first thing to establish about the Dasam Granth is what it is not. Sikhi has one Guru in scriptural form, the Guru Granth Sahib, installed as eternal Guru by Guru Gobind Singh in 1708, and the Dasam Granth does not share that status. It is not installed in the same way, it is not the Guru, and treating the two as interchangeable is a serious error, which is why the atlas keeps them as separate entries and refuses to route compositions from one to the other.
The second thing is that it is nevertheless woven into ordinary Sikh life. Jaap Sahib, the tenth Guru's long hymn of divine names; Tav-Prasad Savaiye, from the Akal Ustat; and Benti Chaupai, a petition for protection, all come from this volume, and all three are in the Nitnem, the daily prayers. The first two are among the five banis recited at the Amrit Sanchar, the Khalsa initiation, at the making of the amrit itself. The opening invocation of the Ardas, the congregational prayer said at the close of every Sikh service, is from the Var Sri Bhagauti Ji Ki, which is also here. A Sikh who says the daily prayers recites from the Dasam Granth every morning and evening, whatever position they take on the questions in the next section.
The volume runs to about 1,428 pages in the standard recension and is extremely varied: hymns to the Timeless One, the Guru's own account of his life and mission in the Bachitar Natak, the Chandi compositions, long retellings of the Hindu avatar narratives, the Persian Zafarnama addressed to the Mughal emperor Aurangzeb, and the Charitropakhyan, four hundred and four tales of deception. It is written mostly in Braj Bhasha, with Punjabi, Persian and Sanskrit.