After a 6,000 mile trip in my 2010 Outback with mixed success with my Nuvi 855 (replaced my 760), I was quite frustrated. Still a relative newbie to GPSs, I still retained the idea that they did everything but wash dishes. On the long straight interstates, it worked perfectly, as the 760 had when doing local (my County) Census mapping. I was impressed with its convenience and accuracy. I'd grown up a Boy Scout and military, being very familiar with how to read maps. But headed South near Denver, suddenly, despite telling it "no toll roads" in the settings, it wanted me to go East to what I knew was a toll road. I ignored it, and drove the Interstate through Denver, quickly understanding why it violated my instructions: lunchtime traffic. Well, it saved me a few bucks, but now I was not quite so trustful. Easy way to Las Cruces with a stopover in Las Vegas (NM), and locally it served quite well. Then another long, mostly bleak I-10 to Houston, but it said I could do 85 mph! No way, maximum on U.S. Interstates is 75! Yes way! Posted speed limit, so I sped up. Pretty straight shot until I got near San Antonio, and it said to take the next right to go left to Fredricksburg. Why? San Antonio had a perfectly good Interstate bypass. Choice: follow the questionnable GPS or trust my instincts? Checked the time, near noon, I'll trust the GPS one more time. Well, it was a mixed blessing, technically shorter, lower speed limit much of the way, certainly full of places of interest, but I was not happy. Got to Houston, and the GPS initially worked fine locally, next day didn't want to give me maps or anything. 2 days later, it was working fine after finding a place to change location maps in the tools. The original instructions with the unit didn't say anything about that. Trip back home was similar, and had to do a change back to home area. Frustration! Then saw this Guide, and figured the 2nd Edition might be more recent and useful than the first, so ordered it. By golly, some of the first things I read were what had frustrated me on my trip! Wish I'd seen this BEFORE leaving on the trip. Lots of good, common sense info, and why you should NOT solely rely on the GPS, helpful as it is. Really opened my eyes to the benefits and the limitations of a GPS. Now I'm more confident in using it, and the GPS is a real boon to my travels (keep up your map updates!), in the car or walking around a visited location. Worth the money for this Guide, especially if you're new to GPSs. Easy to read, and for me to understand. It's the user guide Garmin should have included with each GPS but didn't.