I bought this book upon relocating to DC because, while living in Philly for school, people would constantly tell me that I needed NFT. Ultimately, I used this for little more than a Metro map reference in my first month in DC.
In my opinion, what makes this "not for tourists" is the fact that the authors spend a good amount of time railing against local government and tourists. Apparently, that gives them carte blanche to do a really lazy job on the rest of the book. For instance, neighborhood maps with local businesses (coffee, gyms, nightlife, restaurants) provide only a symbol denoting what category the business falls under, not which specific one you're actually looking at (e.g., a martini glass denotes a bar, but in the Adams Morgan area the map is littered with martini glasses; it's left to the reader to uncover which one pertains to the bar you're attempting to reach). Wouldn't a number system have been the logical route? Also, "reviews" or "descriptions" (whichever they are) of points of interest are limited to 2 to 10 word blurbs. I can't imagine anyone basing a decision on such limited information. These are only two of my larger critiques.
In sum, as an avid traveler who has read through many tourist books, I struggle to see what niche NFT fills (unless you really want to know what time your local post office closes). Lonely Planet covers pretty much the same areas, and does so in much better detail. I can do without the pokes at bumbling tourists (which would be just as pertinent if I were a visiting tourist myself). Do yourself a favor and stick to LP or Google for the best information on a city. I am forever done with NFT.