I just went for my first visit of the Peak District last weekend. Before leaving, I had a read of some of the introductory chapters, which were well written and interesting. The photos are very nice and the top 10 lists of things sounded great, too. The insider tips on the end of each chapter are not really my kind of thing, but seemed like a nice touch. The recommended accomodation sounded really interesting, but we had already booked, so we didn't use that part. Skimming the information part gave us a good idea of what we could see in the two days in the area we were staying, so we went on with the book in hand and a loose plan of what we wanted to visit.
However, when I actually tried to use the guide to... well, guide us to anywhere it failed miserably. The maps are just rubbish, even the colour one, with no details and no reference to the text whatsoever. The town maps are better, but seem to feature mostly shops and eateries. Most of the places described in the book don't feature on any of the maps inside. We only visited a few places in the southern White Peak (including Dovedale and the Stanton Moor), but trying to rely on the guide ended up with driving round the country roads, cursing a bit and eventually following directions from Google Maps - the guide offered no information on how to actually get to the Nine Ladies stones on the moors, and didn't even bother to mention where the entrances to Dovedale are, which is supposed to be one of the most popular areas to visit. I don't even want to imagine where we would end up if we used in in the Dark Peak with much less people around to ask for directions. I never expected it to be a walking guide, but we limited ourselves strictly to popular places where people often come by coaches. The only places with detailed addresses in the guide seemed to be the ones where you get charged at the entrance.
The index doesn't include restaurant or pub names reviewed inside and the ones mentioned don't provide any information if booking is necessary - we visited two of the recommended gastro pubs only to learn there are no places at all and that it seems to be a normal situation on the weekend.
So, to sum it up, it's probably a great guide provided you read it for the fun of it and are not actually planning on going anywhere. Otherwise, I'll probably recommend picking up a "Visit Peak District" booklet somewhere, which actually contains a useful map, and getting all other tourist information on the Internet.