The cover of this guide is a good ice breaker for your trip. Just comment why in the world would they choose it and immediately you will have people to talk to, no matter where in Turkey you are. But don't judge a book by its cover. Lonely Planet is usually the best guide around and this is a good example of that. I spent 3 weeks in Turkey and not once did I feel I needed info not available in the guide. Maps are abundant and contrary to other reviewers, I find that there is enough history for those interested in traveling to learn (it is a travel guide after all, not a history book) [overall I would guess there are say 30 pages of history in the book].
Why 4 stars and not 5? I felt the writers were too enthusiastic about everything, and that made it hard on the traveler to decide what was worth visiting and what wasn't. Let's face it, every location is not the most attractive town in Turkey, yet the authors claim that for way too many towns. So take their praise with a grain of salt and you will be fine. Also, the amount of hours bus trips take are not all that precise. (+-20% in my experience).