The ROUGH GUIDE series has produced some wonderful books -- I am particularly fond of the titles on France and Scotland, which I have used extensively. This is their first crack at Iceland, and it is a commendable, if not outstanding, effort.
As a result of a recent 15-day trip to Iceland, I can say that it is mostly reliable but far from exhaustive. For one thing, the emphasis is on sleeping bag accommodations exclusively. (Okay, maybe I'm not quite so "rough" a traveler: Two weeks in the same smelly down bag is not my idea of comfortable travel.) Also, the book omits many very viable accommodation options, such as the Bolti farmhouse at Skaftafell. Also many oustanding restaurants such as the well-known Bautinn in Akureyri are unaccountably missing.
What did this guide have to say about my guesthouse in Reykjavik (the excellent Baldursbra)? Only that it had "rather narrow beds and unfortunate floral curtains." Good grief! Firstly, the size of single beds in Iceland tends to be quite standard: No extra inches were shaved off. Secondly, the curtains were indeed floral but not so aggressively bad as suggested by the writers of the guide, who appear to have been suffering from a bad hair day.
On the plus side, the "Basics" and "Contexts" sections are both useful and entertaining introductions to travel in this most fascinating of destinations. I've always regarded a good bibliography as an asset to any guide, and this one has an excellent one. Included is a helpful summary of the key Icelandic sagas, a knowledge of which is essential to understanding the uniqueness of Iceland.
You won't go far wrong with this guide, but there is room for improvement in editions to come. For now, I recommend the 2001 Edition of the Lonely Planet Guide as being the most authoritative guide.