Final answer:
The specific series of books Joy brings to Ruthie is not mentioned, and without further context, it cannot be accurately determined.
Step-by-step explanation:
The series of books that Joy brings to Ruthie to read over summer vacation is not explicitly mentioned in the provided references. Consequently, without specific information from the text that the question is referencing, it is impossible to provide a definitive answer.
However, if we reference the provided materials, we could speculate that Joy might have brought books that have a profound impact on readers, similar to the stories of Laura Ingalls Wilder or Rilla of Ingleside by Lucy Maud Montgomery, which could offer a blend of historical insight and captivating storytelling suitable for summer reading.