What are some alternatives?
When comparing Book Summaries and WikiSummaries, you can also consider the following products
Blinkist - Key insights from 2,000+ bestselling nonfiction books
Four Minute Books - Making you smarter in 4 minutes or less.
12min APP - Free reading app for summaries of nonfiction books.
GetAbstract.com - Book Summaries, Book Abstracts
Instaread - Read or hear key takeaways of any book in minutes
BookRags - Apart from book abstracts, Bookrags.