Display posts from subcategory?

Hi guys, I have been working on this for days and any help would be appreciated.

I am using wordpress as a CMS and I am trying to display the posts from a “grandchild” subcategory. The issue here is I do not want to hardcode any category ID’s into the template. I would like one generic single1.php template. I would like it so that we could just add more books in the future by creating a new book category, i.e. “Book C” under the “Books” category and a grandchild category under Book C called “Book C Reviews” where it would display the book in a single1.php template and below the book it would show the reviews for that book.

I thought I could query_posts, but I can’t get to just the “grandchild” category. I appears that I will need a custom function.

The structure would be like this,

Books (parent category)
– Book A (child category)
— Book A Review (grandchild category)

Does anyone have any ideas or can point me in the right direction?

Thanks, Wes