My Outlook and views, hinduism is not a religion in its narrow sense. it is a conglomeration of various beliefs and even atheism. Atheists existed even in Vedic and were known as Charvakas.
There is no single book the hindus consider as "holy-book" like the followers of semitic religions. The teachings of hinduism are spread in hundreds of books.
The Veda primarily dealing with rituals is Yajur Veda and it is mostly about worship of "Indra, Agni, Varnua, etc" Pl read Volga to Ganga to know how the "invisible god" was invented when people lost faith in those concepts. The Christianity and Islam originated much later in history and they also assimilated many of the oral traditions of the primitive tribes. Modern humanbeings are presumed to be originated in Africa and spread to various parts of the world. So there could be some similarities in the beliefs/customs, etc.
