Excellent spot! Pity I bought it at full price!
Anyway, it's a good read with some useful info between the covers. The only thing I would say is that it's very difficult to read on a monochrome Kindle due to the colours used in the eBook. However, once the DRM protection has been removed, it's full colour splendour is revealed and it's an absolute delight to read on a tablet or PC.
At 99p, it's a steal!