Id' put it slightly differently. TT Book 5 is the material which the CAA exam expects you to have studied. It's not really a good book, is confusing in many places, and contains a good number of errors. But, as I say, that's the required material.
MS FS2004 will have many hours too - well worth while.
The key thing about instrument flying is that the procedural learning is done on the ground. In the air, one merely polishes it. That's why a sim is very good.
But I think there are much better books on instrument flight, mostly FAA IR ones.
A lot depends whether the person is doing the IMCR to fly real IFR. If so, best to learn it properly. That also means digging out a good instructor - not many of them around for this subject.
There is a lot more to learn if flying IFR - getting weather is more complex, icing issues, etc. I did a few hours today at FL100, collecting a few mm of rime ice as usual, and could not help reflecting that many/most pilots (and instructors) will tell you that you will die if you pick up any ice on a normal plane... Somebody should do some "real IFR" ground school... whether there would be any takers I have no idea.