The Chessmen is the third novel in Peter May's Lewis trilogy. It feels like and afterthought.
First off, the basic premise is ludicrous - that a loch would spontaneously drain and reveal a plane wreckage containing a dead body. Even less plausible that the people discovering this wreckage would have an intimate connection with the incident.
The strength of The Blackhouse and The Lewis Man was that the story had an internal consistency. The same characters were at centre stage and there was a continuity - a natural progression - in the story. In The Chessmen, we discover a whole new era in former Detective Inspector Fin Macleod's life. He was, apparently, intimately connected with a celtic rock band that became quite famous (perhaps based on Astrid) and spent much of his time at university roadying for the band. He had a number of best friends who were never mentioned in the first two novels in the trilogy and a couple of the cameo roles in The Blackhouse are reprised as starring roles. The trouble is, these characters are not as well formed as those in the first two novels and are ultimately pretty indistinguishable. The storyline - humphing gear and jumping into each others' beds is dull at the best of times, but when we know that Fin was supposed only ever to care about Marsaili, it becomes even less relevant.
The folk stories that had been introduced with a light touch in earlier novels feel heavy handed here. In particular, the Iolaire disaster (pronounced Yu-la-ra despite what Peter May would have you believe) would be well known to everyone on the Isle of Lewis, especially those with immediate family members involved. There is repetition from previous books without ever feeling like it's enough to set the scene for a stand-alone novel. By way of example, there is a story about Douglas which follows on directly from The Lewis Man; it would be meaningless without reading the previous novel, yet we are treated as though characters need to be re-introduced and settings re-described. It's a mess.
Perhaps I suffered for reading the three novels back to back, but I just have a feeling that The Chessmen was an afterthought, tacked on to maximise revenue from a successful pair of novels. Frankly, I wouldn't bother: The Lewis Man is a perfectly adequate ending to the series.