Aha! The Harry Potter books! My impression is that Rowland doesn't work out her plots in sufficient detail before she really buckles down to business. As a result, in all four I've read, about 2/3 or 3/4 of the way through, she has to introduce some hitherto unanticipated element (i.e. a deus ex machina) into the plot so she can start tying up loose ends. It put me off enough I've never bothered to read the last 3 in the series.
It's a rule of good fiction that all surprise developments are foreshadowed. The classic example is the murder mystery on the last page of which Max Carrados announces "the butler did it" and you, the reader, go aha! why didn't I see that: page 2 made it obvious (in retrospect).
Rowland's lack of foresight is similar to that of movie maker John Waters. About the same distance into one of his crazy movies, the plot goes completely off the rails; however, he doesn't do the d. ex. m. trick. Instead, he lets the viewers writhe in agony.
A much more adult series with something of the same flavor is Jack Vance's "Lyonesse" series. Gollancz is publishing them in a single volume in the spring. There will be a pop quiz in May.
