I picked this up last night for grins and giggles, I was blown away by the quality of the book. It's really detailed both factually and in terms of its visual layout. It includes interviews with architects representing some of the biggest firms today, in which they explain their personal connection to LEGO and how LEGO imbues the core concepts of design in children (of all ages!). I will probably pick up a few more sets for play, but I don't see this as much of an investment set for the same reasons others have cited: I think it will be in production for a long time, and the price per brick is inflated.
For those interested in buying this set to explore the concepts of architectural design, I would also recommend the LEGO Architecture book by Tom Alphin. It's a lot less dense than the book that comes with 21050, but for someone with very limited knowledge of architecture (like myself), it gives a quick and engaging overview of the history of architecture. It also includes instructions for small builds that are representative of the various styles of architectural design, which makes it a great companion piece for the set. Even without this set, it works well as a nice little coffee table book.
But you don't have to take my word for it!