What are some alternatives?
When comparing SparkNotes and Instaread, 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.
Resoomer - Resoomer is a software and online tool for text summary: it allows you to summarize and analyze your articles by taking up the important concepts
GetAbstract.com - Book Summaries, Book Abstracts
Hardbound - Illustrated summaries of bestselling nonfiction books
Book Summaries - Great books summarized in 5 quotes (or less) so you can get the main idea fast.