Remember, you don't have to read an entire book for a book to be useful!
Introductions and specific chapters in a comprehensive scholarly book are perfect sources for a big topic like ethnic studies.
In the example below, "What Is All The Fuss about Ethnic Studies" and "What the Research Says about Ethnic Studies" may be very helpful--as may be the entire book! You can download chapter by chapter.
You can view the PDF or epub of the eBook right in your browser without signing in or downloading.