Best Place to Buy Software Engineering books

Hi, im currently looking for best place to buy Software Eng/Dev Ebooks. I see that Amazon is market leader, but when i compare some of it to google play books, the price is far more expensive in Amazon. On the other hand, Google Play books catalog is not as complete as Amazon's. Do you have any recommendation or it is just the way it is (buy cheaper on GPB and buy on Amazon if not exist in GPB)? Thanks