I am on my second Kindle and I really like it. I download books all the time, mainly through bookbub.com. When you order a book through Amazon it is downloaded to the Amazon Cloud and to your Kindle (the device). When you are finished with the book you can delete it from the device but it is still in the Cloud. To permanently delete it you have to go online and delete it there. You can do this either on your computer or by going online on our Kindle.
I notice, however, that you are in Canada. I did discover when trying to purchase a Kindle for my niece in Ontario that Amazon does not have agreements with libraries in Canada so someone in Canada with a Kindle would not be able to download books from his or her local library system. If you plan to use your library system a Kindle would not be good for you. Check out Kobo at your Chapters bookstores on on line.