Not oversized enough to be a coffee table book, "The World of Downton Abby"
is nice little tie-in that manages to squeeze in some nice flippable photos and works best when it's read rather than perused. That is not to say that it needs to be through read: probably best a chapter at a time while nibbling the crusts off of some cucumber sandwiches.
There are a handful of thematic chapters which probe the many rituals and routines of Edwardian manor house living and which comment on things such as how society would have viewed Thomas' homosexuality or free-thinking women. The content also profiles the actors in the roles as well as fleshing out the characters backstories at a level that is almost certainly more substantial that jsut tidbits that you might have just missed in various episodes; these nice profiles give a tip of the hat to the level of thoroughness that creator Julian Fellowes has imbued in the series. A definitely read for fans of the series.