Started this subscription for our older grandson, now 10 years old, about 18 months ago. He has enjoyed all the books and his teachers like them because they challenge his imagination and reading skills by covering topics and situations he normally would not read. His vocabulary noticeably has expanded since he started reading these books. He soon will need the next reading level.
We recently started the series for our 5-year-old grandson. His birthday was too late in the year for him to start kindergarten, so he needs books that will spark his interest in reading. He knows when to expect a new shipment and counts down the days until one arrives. He usually has his parents or older brother help him read one the day he receives it. He sometimes reads excerpts to us via Zoom (we're halfway across the country from where he lives). By the time the next shipment arrives, he can read the previous books all by himself. He hasn't tried to read his brother's subscription books yet, but it's only a matter of time.