Thank God for the Lonely Planet!
Judging by the amazon reviews, I was given the feeling that this particular Lonely Planet is not worth the money, especially not if you are only traveling to Oman and not to the other countries covered by the multi-country guide. So I bought the Rough Guide Oman instead, which I'm in generally very happy with.
I also bought the highly praised German guide ReiseKnowHow and thought that with these two rather extensive guides, I'd be well-equipped for my trip.
Well, let's just say that I wasn't even able to book a hotel in Muscat without the Lonely Planet, because both of my other guides completely failed to give me any sort of impression about Muscat and where to stay. Yes, there description of the various parts of Muscat are good and helpful, and yes, there information is likely more up-to-date than the Lonely Planet. But I had simply no picture of the place in my head after I read them (the Rough Guide still a LOT better than the ReiseKnowHow, but still not as helpful as the LP.)
So, kudos to the LP for giving accurate, helpful and practical descriptions of the different places you are going to see.
It's funny to see some of the other differences that can get people confused: Shiites quarter in Muscat - LP say keep out (as do the signs in Muscat), RG says go. Isreali stamp in passport - LP says you may not get a visa with one, RG says it's no problem ( as says pretty much every other information I found on the web, including the German foreign minstry). Eating in Oman - RG says it's hard to find any decent food, LP says you can good food at every corner.
Layout wise the LP is a lot more structured, with clear, big titles for towns/places, and smaller subtitles for attractions within. There's always a chapter about how to get to and from a place, about eating, sleeping, shopping, always in the same, reliable order. The RG is prettier and easier on the eyes, adding a bit of color with its orange titles and generally more readable font (OMG I'm getting old if the font becomes releveant to me). It's not as structured, though, and some of the places I tried to look up beforehand, I only found when I actually read the whole thing.
Personally, I don't buy travel guides to get exact information about prices or about which cafe offers the cheapest coffee. I buy them to get inspiration and information - helpful hints can come in many forms, you just need to know how to read between the lines and how to take everything that is written with a bit of (your personal taste) of salt. As such, but LP and Rough Guide are good resources.
I'd probably recommend the Rough Guide, because it covers the whole country and as such is more extensive (and at the time of this review more current than the LP).
LP, however, offers the possiblity to download certain chapters of a book from their website. An eletronic copy of the Oman chapter cost a mere EUR 2,45, and if that's not a bargain deal, I don't know what it.
So, if you find yourself traveling to Oman sometime this year, buy the Rough Guide, and then get an electronic copy of the LP, and then make up your own mind.