I have never read or heard anything about that book but I would personally stay away from it because it has nothing to do with the ABRSM style tests. Do you have any workbooks by the ABRSM? There is a good one called "Theory Workbook Grade 7 by Anthony Crossland and Terence Greaves". That's the main one I have. I don't want to put down the composition aspect of the exams, but it's very subjective, and melodies that get decent marks aren't always the ones that you think are amazing! I wrote an awful one for my grade 6 theory, just repeated bars 1-2 slightly differently in 3-4, inverted them in 5-6 and made sure I used the standard perfect cadence chord progression in the last 2 bars! I got 17/20

. A doddle! They do look for originality in the composition etc but if you use standard techniques like inversions, appropriate chord progressions, sequences etc then in my opinion you cannot go far wrong. It's not really like music it's more just learning a series of techniques and using them, I know many people who do what I do and they all get high marks. Don't try to make it complicated, you're not there to be the next Mozart, use the techniques and play the stupid game back with them

. Oh yes, and add in random dynamics and articulation too

Even the theory workbook I recommended goes into far far too much detail for my liking, I never practise composition for a theory exam, I just go by my formula! You might not want to though, and I'm waffling and I doubt any of this makes sense!