The Hindu pantheon is not preserved in one book, and the gods who dominate it now are not the gods who dominated its oldest layer. That gap is the single most useful thing a reader can hold on to.
In the Rig Veda the hymns go overwhelmingly to Indra, to Agni and to Soma. Vishnu is present but slight, and Shiva appears chiefly under the name Rudra, an outsider addressed with care. Move forward to the Puranas and the proportions have inverted: Indra has become a functionary who loses more often than he wins, while Vishnu, Shiva and the Goddess carry the tradition. Nothing was deleted. The older material stayed in the canon and was reread.
The corpus that carries this is layered rather than sequential. The Vedic samhitas, the Brahmanas, the Aranyakas and the Upanishads form one body, transmitted by a discipline of recitation with few parallels anywhere. The two epics work at a different register and reached far more people. The Puranas, encyclopedic and openly sectarian, are where most of the narrative a modern reader recognises actually lives, and where the same story is told differently depending on which god the text serves.
So a claim about the Hindu pantheon usually needs a date and a text attached to it, and a claim secure in one sampradaya may be politely denied in the next. There is also a great deal that no Sanskrit text carries at all: village and lineage deities, worshipped continuously, who enter the written record late or never. The atlas records the structure and does not adjudicate between the centres.