On my visit to Cochin for official purpose, DC books(book store) which I found more than once was the most suitable spot for those who like to choose their read(novels in my case) while browsing through the whole store. The DC books store(the one in Ernakulam) is quite wide which means more books for you to check out from.
Dc book stores had various novels(even older ones which you might not find anywhere else). They(the store staff will point out book sections to you depending upon your taste and budget(I purchased a British author novel).
The best things about this store is that they have decent collection of magazine(brands) as well. The magazines were latest and as per the owner, one could also ask for magazines dated a few weeks back(depending on availability). High MRP novels can also be bought from here(really).
Note: this store is locally popular and hence easy to find. Best recommended for book nerds. Good store, vast variety, a little bit technology driven.