For me, it would definitely have been worth $60. I wish I could buy more - I know DS5's teacher might appreciate it. I paid the regular price ($25) when DD7's testing was done.
In my opinion, Topsy-Turvy Kids is no substitute (I have that too).
Whether it's worth that much to you depends on how much you believe your child is a VSL. I found the whole book fascinating, since a lot of it applies not just to my dd but to my other kids, to two of my brothers and to myself as well. It may also depend on what you are looking for - if you are merely looking for a few solutions, stick with the articles on the VSL website, but if you want an in-depth understanding, go for the book.
that's my two cents
