Auto Summarizer is a pretty handy tool if you want to create a quick summary of your very long articles. The best part of this tool is you can mention your summary length in terms of paragraphs. The summary which is created is totally dependent on how you had made paragraphs and how many places you have new paragraphs since it does not support HTML.
Here is an example of Auto Summarizer. I had used the text from my post on Shadow Explorer . I chose my summary to be in 10 paragraphs and I got this. Well ist long and I should have chosen 6 paragraphs or may be less.
PS: The above image contain those text was created using HideText Tool
This gave a pretty clear picture of how it works. Suggestions from my side is use less number of paragraphs unless you have very long article. The summary what you get might not be very accurate or well formatted, but from this you would get some ground work done and you can edit to fix all minor details. Check out Auto Summarizer