This really is a remarkable set of books - and I'm glad that I was able to purchase them more or less as they came out - as it does spread the financial pain!
For birders in Australia and New Zealand this is the equivalent of BWP - and it is just as thorough. The whole series is split into 7 volumes, with volume 1 and 7 themselves being split into 2 books - thus the whole series contains 9 books. The plates are superb and the level of detail of each species account is very impressive. This is just about as close to a "and this is what we know about this species" as you can get.
If you are serious about having the definitive account of birds of the region, then this is the series you need - although the price is clearly an issue. However, you may need to move sooner rather than later as the final print run of this book has been completed and it is highly unlikely to be repeated.