The biggest concern that people have with online shopping is usually this: Is my Credit Card number safe? People are afraid that hackers might steal the credit card number as it makes its way through the internet.
When you shp with Amazon.com, your transaction goes through a secure server. What that means is that your credit card number, and other details, are encrypted using a secret code. The code is so secure that a hacker with the latest computers would still take millions of years to crack it. Your card number is safe from hackers.
You will get your books I have bought books from Amazon.com several times, and the books always reliably arrive. And I live on the opposite side of the world from them, in Southeast Asia! Amazon.com seems very careful to maintain their good reputation of reliability.
What about personal information: Obviously, to buy books from Amazon.com, you need to provide some personal information, including a postal address and a credit card number. Their "privacy policy" means that they don't give your personal details to anyone else. They also ask for an email address, so they can send you updates about your order. They offer to send an e-newsletter as well, but you can choose not to receive that. Your personal details are safe.
Is it difficult? Not terribly, just select the books, add them to your "shopping cart", then when you've finished selecting books, click on "proceed to checkout", then fill out the forms carefully. When your order is complete, you are done. Your card will not be charged until they actually send the books. Shipping charges depend on where you live and how urgently you want the books.