How do I search iBooks store for free books by category so it is NOT listed just by author?

I have been so excited about the release of iBooks for the iPhone and last night it became a reality.

So in the iBooks store I wanted to look through all free titles by category. Unfortunately they only want to list by author and I rarely note an author when selecting books.

Is there any way of searching a category and having it present like the Featured with an option to filter free ones?

I do not have a specific title in mind and just want to browse.

As always thanks for any advice.