Hi Anoop,
Gald you found it useful. Unfortunately, there is not much authoritative work on VSA. Infact, of all the things you read today about VSA, most have it roots in this book. I cannot say if the same method exists by any other name elsewhere, but a google search does not offer much.
Also, my personal experience is that there are very less takers for VSA compared to conventional technical and fundamental analysis. Having said that, bear in mind that practicing VSA is a bit difficult compared to TA/FA. You need lot of practice. Diligent exploration of historical data is needed some times.
From my experience with VSA till date, this one ebook and sincere practice is enough to trade using VSA. In case you want to pursue it, just post in the "Volume Spread Analysis" thread in "Advanced Trading Strategies". I will try my best to solve your queries. There is also one AFL for VSA by Karthik Marar(who started all this VSA thing in this forum), but I would prefer that you first learn it without the AFL, and then use AFL just to complement your skills.