It can be very expensive to buy all textbooks you need if you are a student, a researcher or just want to learn about something. Also, once you've learnt what you needed, you may no longer need the book and you are stuck with expensive items you no longer need. You can't even re-sell ebooks once you no longer need them.
A lot of textbooks are available in subscription libraries in an ebook format. You can typically access these with a monthly fee, saving you up to several hundreds each month. It can take forever to browse through the internet for deals and to find if each ebook is available in subscriptions like Scribd or Perlego - you can however just search on eLibSearch for all the books you need - you will see availability from different sources in a matter of seconds.
Once you found the services you need, just sign up and start saving. Often you will also get a free trial, as well as access to hundreds of thousands of fiction and non-fiction books you might want to read in your free time.