The best Hinduism books split into two kinds, the sacred texts themselves and the books that explain the world they came out of, and you want one of each. Neither order is wrong, but picking the wrong one to start with is why so many people put the subject down after twenty pages.
Easwaran's Bhagavad Gita works for almost anyone opening a Hindu text for the first time, because its introductions carry you through the parts that would otherwise stop you. Someone who would rather understand the whole tradition before reading any of it should take Hinduism: A Very Short Introduction instead.
Some of these are the founding Sanskrit texts in English; others are the epics that carry the same ideas as story, and a few step back and describe how it all fits together. Difficulty varies far more than length does, and none of it assumes Sanskrit or any prior reading.