I’ve read about half of it. Some parts interest me more than others. It has clearly titled chapters which allow you to read the parts that interest you. I found the chapter on Britain and the chapter on the Standfast movement interesting. Plus it includes a number of biographies that can be read in any order. There’s a definite attempt to rehabilitate Paul Johnson, for example, after the probably distorting criticism of him in the Watchtower over the years.
It has a number of interesting appendices too, including a testimony from an old Swedish brother on what it was like to work at the Headquarters under Rutherford. Did you know that not all workers at Bethel in the 1920s were even baptised? Some just applied for the work and were accepted because they needed workers.
You can find videos with the author discussing the book on YouTube if you search for Rud Persson and Watch Tower History.