It's sad to see a well-loved series bog down - I really enjoyed so many of the earlier books, they were enchanting and magical and a real pleasure to read. But, alas, the magic faded somehow...
Btw, reading your post to Enthusiast above about a Canadian detective traveling to Scotland - ironically, I do believe it's possible that you might be thinking of Penny's second to last book, The Long Way Home. Gamache travels to Scotland to visit the Garden of Cosmic Speculation seeking clues to the whereabouts of the missing Peter Morrow. Does that ring a bell? 
As for Peter May, he's written nearly two dozen books, but the only ones I've read are the three in his Lewis Trilogy, which all take place in the Hebrides. I thought they were quite wonderful - although I must confess I probably liked the first one best. But I do recommend the whole trilogy, it's a fascinating look at a very unusual part of the world with a very distinct culture.
I will certainly post my take on Entry Island once I've read it.
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