This WOULD have got a four; it has the same tight plotting and interesting twists and turns as the original, BUT... I had to knock it down one because the viewpoint character is SUCH an annoying arsehole. I genuinely came close to giving up on the book a couple of times because he makes it so grinding. 
 However, I'm glad I didn't because the final third of the book is very good indeed, and the very last line is a stonking cliffhanger; so stonking I'm off to pick up book 3 right now.