I have bought many books from flipkart. The delivery service has always been a good experience. There was never a missed book or late delivery. But I would rate it as a "somewhat" satisfying experience.
They sent me a promo code one day and when I tried to access their customer service email ID to get some clarification on it, I got back a very curt/rude response and also got a call back which was equally insensitive/distasteful; forget resolving my clarification. It virtually drove me away and I am no longer purchasing anything with flipkart. Many times, a foul mouthed, insensitive CS can drive customers away - that is what has happened with me too, I guess.
Still, site is good for delivery as I said - so I would recommend ONLY for buyers who may have had bad experiences at other places (I’ve had some - and found this flipkart better in comparison), because there is still one aspect, the CS, where they need to cover miles.
In any case, there’s probably nothing like buying from a bookstore though.