Currently, it's not advised to book the Bajaj Pulsar NS400 before its official launch. Typically, bike bookings open closer to the launch date, and manufacturers announce the booking details officially. Bajaj Auto will communicate when the booking process begins through their official channels, such as their website and social media. It's recommended to stay informed by regularly checking these sources and contacting authorized Bajaj dealerships for the most accurate and up-to-date information regarding the booking process.