When I travel, in any country, I use Lonely Planet- including the country I live in, Morocco. It is a good book, very helpful, and very popular. Perhaps a little too popular.
This is now my third Lonely Planet Morocco. I've used this particular edition to travel to Melilla, Shoofshowen, Meknes, Walili, Mulay Idriss, Shalalat d'Uzud, Marraksh, Warzazat, Ait Benhadu, Sfru, Bhalil, Taza, Ifrane, Gouffre de Friwato, and my hometown of Fes. And I have found that it helped me find some decent hotels, figure out travel plans, and where to eat. But not as much as it once did.
Others online have remarked on this- the Lonely Planet Effect. It seems to be in full force in Morocco. As soon as a transportation method, hotel, or restaurant is mentioned in Lonely Planet, the proprietor will cut out the bit where he is mentioned to post on his wall, and jack up the prices- significantly. So though the book just came out, and was only a few months old when I began using it, nearly every place I go the prices are no longer what is listed. Now, this isn't LP's fault, certainly. But it does make the book less helpful than it once was.
I've now taken to using LP just for the maps and travel suggestions. When I arrive in a new town, I look for any hotel that is *not* listed in Lonely Planet, and try to find someplace clean. Those are usually the affordable hotels. Any place mentioned in LP is far out of my price range.