I really agreed with you! Charlie is the most trouble-free child in the universe - he never impinges on Isabel's existence, it seems. I wonder whether McCall Smith wrote a pregnancy in for Isabel in a hasty moment, to provide a twist at the end of one of the novels, and then subsequently regretted it as poor old Charlie is just totally ignored. She worries about Jamie all the time but IMHO Jamie's quite a dull character - I can't quite see the big attraction. Sorry Jamie... it just seems odd that Isabel has focused on him THAT much for so many years, in real life I suspect his charm might have worn off.
I've always loved this series and think they're great, but the mysteries in them are usually pretty gripping and take centre stage, with Isabel, Jamie et al providing an intriguing back-plot. In this one the mystery is a bit half-hearted and the rest doesn't seem to sustain a book quite so well. Isabel is a lovely character but she is independently wealthy, loves her job (and is her own boss), has a housekeeper who seems to act as a nanny too, has a younger man who adores her and is able to spend her time at concerts, galleries...pleasing herself basically. She has a pretty trouble-free life and I find it hard to be TOO sympathetic over her agonies about Jamie talking to a composer who she thinks is a bit odd. Get a grip, girl! (oh, and by the way, Isabel, also stop helping Cat with that deli every five minutes. she can hire someone)
I also agree with your last paragraph, though, Julia F; he is a lovely writer and I still enjoyed the book - I just thought it wasn't as good as the rest.