S.W.
dear M.,
personally, i think that this sort of thing is a waste of money and resources. my DS spoke and read earlier than most but i believe (and his ped agrees) that is because he lives in a very verbally and book/magazine oriented home.
i think the best way to teach such things is more naturally, by reading to your kids and around your kids and simply immersing them in a very natural manner. to me, kids today are already bombarded at every turn with electronic stimulation and learning to read by increasing such input seems counterintuitive.
i can't speak to the specific series and i DON'T mean to lecture. these are simply my 2 cents. i hope they find you well.
best of everything to you and yours,
S.