What is the Sharʿī ruling on purifying contaminated books—some of which do not belong to the questioner—as well as contaminated land and tools? Is it obligatory to inform one's family about this, and what are the consequences of not doing so?

What the questioner mentions are mere whisperings (waswas) that have no reality. Therefore, one must turn away from them and not pay attention to them, and not rule something as impure merely based on doubt, in order to avoid falling into hardship due to the whirlpool of whisperings.