The books have the same gentle, almost whimisical, atmosphere as the Precious Ramotswe books. McCall Smith has a way of evoking large settings through the emotional insights of his characters (rather than through blatant description) so that the #1 Ladies' Detective Agency novels always give me a sense of vast skies and hot days and slow-moving cattle, even when McCall Smith isn't describing the vast skies and hot days and slow-moving cattle.
Unlike the Precious Ramotswe books, the Sunday Philosophy Club books take place in Scotland (Edinburgh) and have a European feel to them (more European than British, interestingly enough), although I always get a sense of sun peeping through uncertain rain clouds (which seems more British than European). And the Sunday Philosophy Club books don't really have set-up/pay-off mysteries. The Precious Ramotswe books usually do have a few puzzles--if no complex, Agatha-Christie-like corpses. I found this lack of crime a tad annoying at first, and I still feel that the books are wrongly genre-lized in the libraries. I have found, however, that if I read the Sunday Philosophy Club books as gentle dissertations on the oddity and complexity of human problems, I'm fairly well satisfied. They are the kind of books you can read before you go to bed (and I am usually opposed to the use of literature as a sleep-inducer) or while you are eating. I don't mean to imply that the books are boring. They are, rather, very soothing, like having a quiet, yet absorbing conversation with a very relaxed orator (who might even speak with a faint Scottish burr).