This guide came out just before I set out to Iceland, and thank G-d for that because I wouldn't know what to do without it. As usual, RGs are the best guides around, beating the competition hands down. (In this case I only found another guide to Iceland and it was very good - Insight to Iceland. It's full of great pictures and has a lot of information, though not as much as the RG).
Almost all of the information you'd need to travel around the country is there. Unfortunately, some of it is completely incorrect. For example, I found it quite disconcerting to be effortlessly driving through some roads that it said would be muddy even in the height of Summer. Or to be paying (much) higher prices for some attractions than stated in the guide.

This guide is good and though not to the RG standard I've been used to, it is still better than the competition. But the authors must do better to fix these minor, obvious, mistakes...