I used to have a membership with the Mystery Guild, just to collect these books and a couple of other series. I quit when they started piling up unread.
I was hoping to start up collecting them again with my Reader, but I found they didn't start until "P". I happen to have all of the books up to "O", so I'm good, even if "P is for Peril" costs twice as much as the other later editions.
(For some reason the Sony store had "Q is for Quarry" on sale, so I bought it.
)
I haven't read them in a long time so I started at the beginning a few months ago and found that I don't really care for J - M.
I'm reading N for the first time and I'm not that excited about it either. I've read good reviews for "O is for Outlaw", so I'm looking forward to getting to that one!