It isn't a major player at all. Indian Post Office is mostly used for sending documents and stuff and people prefer it because it's cheaper and available in most destinations ranging from metro cities to small villages.
Most ecommerce players use private logistics companies like BlueDart, DTDC, etc. They use Indian Postal Service only for rural orders where BlueDart and the like don't service.
That's right. Most of these books have a developing country edition (that's what one of my books' cover says). Though most of these economical editions aren't of the same quality as their original counterparts. The printing is mostly black and white and the paper quality is much inferior.