Previewing an EBL title without downloading
If you just need to use the eBook during a single session to browse or use for research, you don't need to download it. Each vendor allows an online preview that allows you to browse the book without downloading it or moving it to a device. This is useful if you are browsing books for information as you might a journal article. Most vendors allow some cutting/pasting so you can move limited content to a Word document for saving or printing.
When you click an EBL title, you have to start with Read Online.
The preview allows easy browsing through a clickable table of contents (which will usually have an index), navigation arrows, and keyword searching within the book.