I don't have a strong of what middle schoolers might consider too easy or baby books, but three excellent Red Sox children's books (make sure to use the SoSH Amazon link above!);
- 86 years, The Legend of the Boston Red Sox. Written in 2005, depicts generations of families watching games.
- There Goes Ted Williams, a beautifully illustrated book that covers Ted the hitter, the war hero, and the icon.
- Growing Up Pedro, because Pedro.
I got most of my Sox history orally, and from the radio/television broadcasts. I honestly can't recall the last time I saw Buckner, Dent, or Pesky in '46 (praise be to the 25). Now that Boone is in the media they find reason to play his homer... that'll actually be a fun story for you to tell. Around that age, I recall being into autobiographies. I read My Turn At Bat, but I recall it being boring. I really should re-read it as an adult. I Never Had it Made (Jackie Robinson's autobiography) obviously has mature themes, but I strongly recommend it.... especially if the kids have seen 42.
Edited to add: The Teammates! How did I forget that?