Do you know about Simple English Wikipedia? Written using "simple English words and grammar" and with over 86,00 articles Simple English Wikipedia is designed to allow readers the ability to understand the topic.
It also allows you to make your own book, that you may download as a PDF or ODF. Using "Create a Book" you may add pages you are viewing or all pages in a category. You may also rearrange the pages. To access Create a Book click on this link:
Via Beth Dichter