Having lived in West Germany during the early 80's and having travelled all around the warsaw pact countries, including several trips to Berlin and East Berlin, Checkpoint Charlie, the wall, etc. etc., I found the bulk of the book quite Interesting.
Without that personal attachment/experience however, I think the book would have been much less interesting. The first 1/3 of the book is roughly a background of the Stasi and it's chief. Necessary information to be sure, but pretty dry. The next third of the book might as well be a hundred or so newspaper clippings. That's how it reads and it's very disappointing stuff.
The final third deals with the DDR's direct support of internation terrorism. This is fascinating and really deserves to be a book of it's own.
Stasi: ... suffers from uneven editing and many grammatical errors -- missing 'little' things like the, a, an from time to time. Also many figures are given in Deutche Marks, and a conversion to $US. This is fine (even helpful!) but the author appears to have used different exchange rates depending on when the money changed hands. Many of these seem accurate, although a few times the DM appears to have been worth $2-3, which I found somewhat suspect. An appendix listing the exchange rates used at different times would have been helpful.
In short, a decent introduction to the Stasi, but don't look for much material about the DDR itself. Almost everything deals with foreign intelligence operations. This would have been a much better book if there had been more material about daily life in the DDR under the Stasi.