So I did pick up BotB this weekend, if only because I really enjoy the idea of siege warfare, and was really, really pleased. The book, as with any of the recent WHFB books, is gorgeous; it's full of color, thematically written, and contains a good number of scenarios, etc.
I've only read through the Campaign portion in passing, but it looks to be very fun and flavorful. Lots of different armies involved in the skirmish, with the Dwarves really being one of the main features. Two Skaven clans are also involved, which was of great interest to me as well.
The siege rules, quite frankly, look like an absolute blast to play. I'm very excited to try them out, as they simply look fun. Additionally, the underground fighting rules look like they're going to provide for some really interesting close quarter scenarios (the board setups are really varied, which i very much liked).
Again, these are just quick impressions, and a full review with pictures will come, but I have to say I'm very pleased with the book. Seems more than worth the $30.
I'd love to hear other thoughts, or any questions you'd like me to direct my book review toward for tonight. Cheers!+