Samples are free and easy to get when you are browsing for books on Amazon. When you find a book you want to check out further, choose Send sample now in the Try it Free section of the page the book information is on (below the Add to Wish List button).
If you like the sample and want to purchase the book, press the menu button while you have the sample open and you will see the option to purchase. Once you purchase the full book, a new complete book file will be delivered to your Kindle right away. At this time, you can delete the sample file (unless you just want to hang on to it). Before you trash it, make a note of the location number at the bottom of your Kindle screen at the end of the sample so you will know where to go to in the complete book. Click the Home button to see all your books. Toggle the 5-way switch to the sample book. When it is selected, toggle the switch to the left and choose Delete. Then you can select the new complete book and continue reading.
If you know the location number where the sample ended, you can go to it quickly in the complete book by pressing the Menu button, then toggle the 5-way switch down to the words Go to Location. Once the words are underlined (selected), press in on the 5-way switch. A box will appear at the bottom of the screen where you can type in the number. Type it and toggle to the right until the words go to are highlighted. Press in on the 5-way and you will be as good as there!
