Winner! and Recapping in Series

Well, the entries were counted and thanks to a random number generator, the results are in. The winner of the signed copy of The Pea in Peanut Butter by Allyn Stotz is:

Anne E. Johnson

Congratulations! Please email me with your mailing address so we can get your book to you.

For those of you who didn't win, you can get your own copy of The Pea in Peanut Butter on Amazon or through Allyn's website. 

Now on to today's post. Since I tend to read a lot of books in series, I'm wondering how much back info should be in each book after the first. The first book sets everything up--the characters, the plot, the conflict. But with series the story doesn't end when book one does. It continues in other books. So then how much info from book one needs to be recapped in books two through... whatever number the series goes up to?

Here's the issue, for someone who begins with book one and reads through, you don't need much recap at all. They know the previous book. But what about someone who picks up book two or three (or in my case book four--yes, I recently did this) and begins there. Some recap is necessary. But how much is enough and how much is too much? And should all the recapping be upfront or is it okay to leak things into the story as it comes up in the subsequent books?

Can you tell I'm working on book two in a trilogy right now? I have a beta reader going through the manuscript and she believes there should be more recapping and that it should all be upfront. I'm not sure I agree. So I'm asking you.

Is it okay to only give the essential info, pretty much the bare bones of book one, and to give a little more later as it becomes necessary to mention it? Or should you do a little info dumping upfront and get it out of the way?