You can try the on book shop.
Many shops at Janpath too.
And if you are interested in online reading I suggest buy a kindle
Ebook is definitely much more easier to buy and you don't have to wait for it's delivery. But if you wish a paperback then Amazon is a great option.
There are many book stores in cp
Visit daryaganj book market, nai sarak.
Online is best in today’s time
Try online on Amazon and flipkart. You can also check out books stores like Om book shop, CMYK bookstore, Bahrisons and Oxford