@Rikki: There's a sample chapter download, and a book download. Gotta find the proper link.
@IAIHMB: I agree with this. The book is copyright 2004, and I think they should have waited another year (3 in total) before releasing it as an eBook. Three years is a long time in relation to technology, and since PHP6 will be all the rage simetime in 2007 (or is it slated for 2008?), this book will be a bit less useful, though the concepts still are important.
O'Reilly waits either 3 or 5 years before releasing their books as eBooks (once they're out of publication) and I think that's probably the best bet.
It could be that their sales just weren't as good as they hoped too. Who knows.