Designing Data-Intensive Applications discussion

Having been obsessed by normalisation and rigorously enforcing referential integrity I am now beginning to find in the real world for lots of reasons, especially performance, derived and summary data, etc can become very important.

Does this book discuss this subject in any detail.

Additionally there are real world situations where certain data is in separate database where one begins to think these two databases ought to be one. Is there any subject matter that would help in making these kinds of decisions, pros, cons etc etc. ?

Seriously considering getting this book.

Many thanks.