The stories also come in pdf format so they can be printed off for classroom use, (just in the case of the odd situation where your school or classroom is having computer issues).
Try enjoying the Math Maven Mysteries right now!
P.S. - There are varying degrees of difficulty, which will obviously depend on your own students' language and math proficiency. If i had to indicate a grade range i would say the easiest problems can be solved by late primary students with the more challenging ones appropriate for the high junior/low intermediate level.