Reddit mentions of Sea of Poppies

Sacred Games by Vikram Chandra is a wonderful, sweeping epic set in modern day India, but with flashbacks to the sixties, seventies and even partition (in 1948). Taking in organized crime, Bollywood, nuclear terrorism, political and religious fundamentalism, social commentary and more. I loved it.

A Suitable Boy by Vikram Seth is a huge (huge!) modern classic that beautifully encapsulates the social mores of modern India as it tracks the trials and tribulations of four families and the search for a suitable bride for the heroine. Simply wonderful. Did I mention it was a big book?

A Case of Exploding Mangoes is a fictional account (one hopes!) of the assassination of President Zhia of Pakistan. I know you asked about India, but in many many ways both India and Pakistan are inextricably linked.

Sea of Poppies is the first of a projected trilogy set in 19th century India. Full of wonderfully evocative language.

Many have already recommended Midnight's Children by Rushdie, perhaps the most important work of Anglo-Indian literature so far. Please also consider his Satanic Verses. The God of Small Things by Arundhati Roy is a lovely short novel.

There are many many more.

Good luck!

I also really loved A Suitable Boy. I think it's brilliant.

For a completely contrasting look at India, I recommend the white tiger by Aravind Adiga.

I think The Brief Wondrous Life of Oscar Wao is absolutely brilliant, one of the best novels of the last decade.

White Teeth is another really wonderful book about multiculturalism and immigrant life that really stands out.

For a rip-roaring old-fashioned adventure yarn, you can't do better than
Sea of Poppies.

Finally for some superior storytelling and brilliant narrative experimentation try Cloud Atlas or Ghostwritten