I can recommend Trevor Thom's book too. As a PPL I have just completed my IMC Rating as I always wanted to try ILS and general instrument flying. Plus, it can be useful to get you out of a tricky situation when flying VFR
Great fun and once you have done it a couple of times and understand what is going on very enjoyable. The most satisfying moment if going visual at DH and seeing the runway dead ahead.
The Rookie.