Why was the doomsday book useful to William. why is it useful today?

The Domesday Book was useful to William the Conqueror as it provided a comprehensive record of landholdings and resources in England, allowing him to assess taxes and allocate land effectively to his supporters. It strengthened his control over the newly conquered territory by establishing a clear understanding of wealth and power distribution. Today, the Domesday Book serves as a vital historical document, offering insights into medieval society, economy, and land use, and is a key resource for historians studying the period.