We used the fairly new Iceland book on our recent short layover in Reykjavik (one of those IcelandAir deals - wanted to see if we liked it enough to go back - answer is an emphatic yes!). The book was extremely helpful. I know the Driving section in the book goes over the rules of the road and warns about the traffic cameras, but I think it is worth emphasizing here as well that they don't fool around with the speed limits and fines. We had heard "horror stories" about people getting $400-800 in fines added to their rental car bill after they were long gone from the country. We were extremely careful, and so far so good on not getting any surprises.
As our time was limited, two full days, we only did the short walking tour of Reykjavik, a puffin cruise, and a drive along the south coast to Vik and back to Reykjavik. Also drove around the Reykjanes peninsula before going to the airport. The book (as one might expect) details the route options and sights very very well. Looking forward to going back and spending more time there, book in hand.