This is a nice progression from the previous sets. It follows along with what they are learning in school. The only con: I'd prefer one book to focus on one long vowel sound and its multiple spellings. When we were studying long E, I had to use 2 different books, one for ee and another for ea and e_e. "Joe's Toe" has Long O spelled oe, and long I spelled i_e. "Chickens" was much better, it focuses on Long A spelled ai, ay, & a_e. I wish they were all more like "Chickens."
You might also want to look at "Now I'm Reading: Amazing Animals" in addition to Bob Books Set 5. Each book focuses more on the multiple spellings of each long vowel.