In this case, free modifies both.

Frank Turk, over at Pyromaniacs, is offering a free copy of What He Must Be …if he wants to marry my daughter as part of his review on the book. I was browsing amazon a couple days ago and happened upon this book, and from the skin it looked pretty good. Not knowing anything about it, or if it was really worthwhile, it found its way into my wishlist until I learned more, and I ended up buying Right Thinking in a World Gone Wrong and If Animals Could Talk along with a student bible to test its appropriateness to hand out at Youth Group as a prize.

Even if I don’t win, it seems like a book that might actually be worth the ~$11 from the review.