I have used Flipkart’s service twice in Bangalore. I had ordered books which were not readily available on a couple of big book stores. On both occasion the books were in stock with Flipkart and were delivered as per promised time (3 days). Got good discounts of ~30% on the books as well.
They have a huge collection and the best part is that they offer Cash on Delivery (which I prefer for all services and helps me avoid lengthy follow ups in case of non deliveries). The books were packed very well to avoid any in transit damage. No issues with billing, time of delivery (Delivery boy called up co ordinate as per my availability).
Overall good experience, recommended.