_Take Your Kids to Europe_, 7th ed. Nice stuff, altho aimed at school age kids (6-16). Advocates traveling as a family, out of the country, to Europe for an extended period of time. Some of the rationale for the details is, well, very white middle-class suburban. And of course the whole thing has limited utility for traveling with an infant/toddler/preschooler. That said, a goldmine of information, particularly the camping, home exchange and home rental stuff. I knew about family rooms at hostels, and as near as I can tell I'm as good or better at finding interesting stuff to do/shopping and cooking overseas/navigating overseas than the author was at least at the beginning. I've gotten many a chuckle out of reading a description of something the author discovered for the first time overseas -- that I can name several instances of in the US. Whatever.
Biblio/resources list is pretty good. It was especially nice to find a relatively complete list of guidebooks-for-families and menureaders, having just gone through the process of researching those myself.