More than just a guide book, this is a book written by architects about the architecture of Prague, starting at the earliest known dates and moving forward to the 1990s when the book was written. It is lavishly illustrated and the descriptions are detailed enough to assist in identifying the buildings and their locations.
I found it useful to read it in reverse, starting at the end and working forward chapter by chapter, this has the effect of peeling the layers off the city one at a time and revealing what lies underneath each addition.