The plot was entertaining fluff, and Donna remains magnificent. I'm getting a little tired of the "Doctor meets literary figure and he and his companions inspire his/her later work with their knowledge of it" trope, which we got in "The Unquiet Dead" and "The Shakespeare Code" before this.
I was stunned reading Wikipedia and seeing that Tennant suggested Wolgar for Christie after working with her in Bright Young Things. I didn't know Tennant was in BYT (which I saw in theatres when it first was released in the States, and of course before I had any conscious awareness of David Tennant), and that's one of a thousand reasons why I really should have that film (which I adored) on DVD.
But I gotta say my favorite part was the trailer for "Silence in the Library," which will air a week from tomorrow on the Beeb. Not only is it the first of a two-parter written by The Great God Moffat, but it also guest stars both Alex Kingston and Colin Salmon! I may geek out all over the place................