I can't think of its title because I haven't seen the episode lately (or I could just look this up), but is the book that Dr. Willis was reading an actual book or a made-up title and plot?
Either way, Danny Wells' bookseller character makes it sound very interesting, so I'm sure plenty of viewers have gone looking for it, especially online.
Grant, the book "The Transformation of Mrs. McTwig" was not a real book. Its outlandish plot, however, was clearly inspired by a real book—Paul Gallico’s 1958 comic novel "Mrs. ‘Arris Goes to Paris," about a London cleaning lady who, after unexpectedly coming into money, travels to Paris to buy a Dior dress—and endures wacky adventures and romance along the way. Though I don’t think it’s while on safari with a Russian midget.