My rating: ★★☆☆☆
Consider this a review of the entire series.
The back covers list the recommended age of this series as Kindergarten to Grade 2. That is absolute nonsense. An accurate reading level of these would be Preschool to Kindergarten.
I wouldn’t recommend these to anyone over five; these are very short books written in the most simplistic way possible with only the most basic vocabulary and grammar–not at all what I’d expect of a seven-year-old. This series is for children at the beginning of the learning to read process, not for children several years into schooling.
On the other hand, this is a very basic, very simple mystery that would hold the attention of a young child learning to read. Five-year-old and younger Scooby-Doo fans will likely adore the series, though parents will likely find it rather boring.