Looking for books/activities to supplement

[HIU8]

DD decided that since DS can now read that she can also. She started the Bob book series and has done books 1-5 twice already. What is out there that I can supplement with? FWIW, this is completely led by DD. I am not pushing her to learn to read, but I do see that she is really interested and capable and I would like to have things that are fun and can challenge her. She is doing site words with DS b/c she thinks it's fun. Other than that, please tell me what you have used.