Conditionally free product?

I've done a search on this and turned up a lot of info on free shipping issues, which was helpful, but nothing on my immediate problem:

We have a small product which costs $2; if this product is ordered with any of our book products, it is free. "Books" is a custom category under "Products, General" and contains 5 products.

The product I'm talking about is a sampler set of 1 each of 10 brochures, classified under our "Brochures" category; it should be free with any book order, but I don't know how to make ZenCart do that. I suspect that somehow I do this with attributes but my attribute knowledge is very sketchy indeed.

Has anyone successfully done this? Ordered by itself or with one or two other items, the product should cost $2 (which includes the shipping; I figured that one out based on a forum post!) Ordered along with any of the 5 products under "books", it should be free.

Help??

You can do this kind of thing with Better Together.

Thanks for the suggestion - I'll look into that. Since I'm still running ZC 1.3.7 I shouldn't need the patch.