The third book (The Well of Lost Plots)... just got silly. It takes place almost entirely in the "book world" thing, transforming this fantastic thing into the routine. Every third page introduced a new plot device, and the plot really felt like it had little direction to it.
Something Rotten came out really, really fast, from my reckoning. Though, it does sound like it might be a return to the earlier novels' style... I'll probably give it a chance; lots of series stumble for one book and then get back on track, don't they?