I found this travel guide very helpful and practical during our one week-long stay in Budapest. As with all the other guides in this series I have seen and used (that is, the corresponding guidebooks on Paris, Berlin and Vienna), there is everything you need to know to plan a successful visit: abundant and easy-to use information on a good selection of sights of all kinds, including museums, monuments, churches, public buildings, famous streets, and so on; a hotel and a restaurant guide; plus all kinds of useful info on, for example, what and where to eat and drink, how to travel from/to the airport, where to shop, etc. For my purposes, I found this information (or the parts of it that I read and used) both accurate and useful.
I was suspicious about the recommended restaurants section, as I had some really bad experiences when relying on the corresponding section of the DK Eyewitness Paris guidebook. But this should be no serious issue, as I found that there were no problems whatsoever in finding great food in Budapest (Paris, it seems, is mostly spoiled in this respect by the vast hordes of tourists that visit the city annually, attracted by that city's quasi-mythical status and reputation as the world's tourist attraction no. 1). Some of the restaurants we visited were mentioned in the guide, others were not (you should also note that the restaurants of Budapest are well represented on the Internet, so it might be a good idea to do some Googling before your trip to find some worthwile restaurants NOT mentioned in the guide).
Visually, this is an engaging book to read, as are indeed all the other DK Eyewitness travel guides that I have read (see above). The wealth of illustrations, including the street maps and floor plans of famous buildings, really enhance this book's usability. Although many of the photographs are rather small, their quality is quite good throughout. In addition to the usual street map section, this year's version also includes a fold-out map of Budapest, which is a nice and useful bonus.
Just remember to use the most up-to-date version of the travel guide, especially if you want to use the hotel/restaurant/café/bar section of the book. The other sections are more time-resistant: for example, there are lots of information about the history of both Budapest and Hungary, which gives you the necessary background info to get the most of your trip.
If you are planning a trip to a big city like Budapest, you should also bear in mind that there are always a lot of more things of interest in a big city that can be included in a travel guide, however good. So keep your eyes open when roaming the streets - it is never a good idea to spend your holiday entirely "by the book"...