This is the only official tourist information centre outside the airport. Ignore touts who (falsely) claim to be associated with this office. Anyone who ‘helpfully’ approaches you is definitely not going to take you to the real office. It’s a useful source of advice on Delhi, getting out of Delhi, and visiting surrounding states.
The office has free Delhi maps and brochures, and publishes a list of recommended agencies and B&Bs. Come here to report tourism-related complaints.