My first impression after reading was 'I have absolutely no idea what to think of this' and it took me a while to figure out why I felt so confused. Eventually I realized it was because I had never seen a detective in a crime-series having been so terribly wrong before. Really. Morse does spent most of the time being extremely wrong: he has a theory, a new clue appears that makes it clear that it can't have happened this way. Another theory. New clue. Repeat almost endlessly.
However these wrong theories aren't comnpletely wasted, many have just a tidbit that isn't completely wrong and collecting all those tidbits finally leads to the real solution (as it turns out he was wrong about having been wrong at one point...) However at no point it feels as if Morse is just aimlessly bumbling along, having no idea what's going on. His theories all make sense at the time. You might accuse him of always looking for the more complicated solution but then the actual solution is somewhat complicated (and it's not like Sherlock Holmes ever went for the easy solution, he just ended up being (almost) always right the first time).
I did like it but it was a bit too much and too concentrated towards the end. At first they had a theory, folowed up leads for a while, found something that disproved the theory, tried another theory. On the final 50 pages or so they just had theory after theory that got often got disproven only a few lines later and that did eventually get a bit riddiculous.
Overall one of those books where I want the half-star system because this was defenitely more than three but not quite four.