We returned in Feb 2003 after 3 months of independent travel in Turkey. We were there mostly to visit archeological sites and ruins, and we traveled with several other books. Nothing, however approached the exhaustive, invaluable and often overwhelming information that the Blue Guide provided us with.
There are many guidebooks that provide basic information on accomodations/restaurants/etc in TK for the casual tourist who will primarily be visiting Ephesus and the other major sites on the Aegean Coast of Turkey. There any book will do, and if you are traveling with a TK licensed guide this is one of the books that they will have had to master in the grueling University program that allows them to become licensed tour guides.
But if your interest in Asia Minor takes you even slightly off the well-trodden path, the Blue Guide is indispensible. I can't imagine understanding places like Boazkale,Seleucia, Letoön, Xanthos,Iassos,Miletus, Stranoniceia without either this book or a licensed guide.
There is often little in the way of informational signage at the important yet lesser visited sites, and compared to other countries ,there is little published information available in book form at the sites other than glossy tourist-photo books.
I can not recommend the Blue Guide too highly to the specialist visitor to Turkeys rich archeological past.