Sometimes you love the first book or three in a series, but the follow-ups fail to engage or you simply lose interest. Which series have you given up on?

I enjoyed the first 3 Earth's Children books, despite some flaws. The 4th was just one walk-and-shag fest, so I was never tempted to continue.

The first 6 or 7 Stephanie Plum books were entertaining, but they started to repeat themselves and I finally gave up at book 12 (was loaned them by a friend -- would probably have given up earlier if I'd been buying them myself).