To Nini 74 and Emmabro,
Regarding sales in England of Rome With Kids: an insider's guide--the publisher tells me any bookstore will be able to order it for you soon. I guess, since it's not officially on the market until July 1, the ISBN number may not be fully in the system yet.
You can always order the book from Romewithkids.com website directly, which is shipping all orders now or,
You can buy the book in Rome; It is currently available in these two major English-language bookstores:
1) The Lion Bookshop, Via dei Greci, No. 33/36, (by the Spanish Steps).
2) The Almost Corner Bookstore, Via del Moro, No. 46 (by the Ponte Sisto).
I also know Barnesandnoble.com are taking orders now, but don't intend to ship until mid-April. After June it will be easier to find in the system. (I hope!)
I really appreciate that you made an effort to find the guide. If you do happen to order from the Romewithkids web site, please mention your tripadvisor name in the notes section.