I once said I would never buy a Lonely Planet guide again, so disappointed I was with their Iceland and Greenland book which was poorly researched, inaccurate and full of rabid anti-American rhetoric.
For my trip to Ghana, it was, however, a choice of only three books available: a semiprofessional Bradt's Ghana (not a guidebook really, more an amateurish newsletter), supremely boring Rough Guide or Lonely Planet. I bought them all in the name of research.
I would say Lonely Planet is best of them all, although certain chapters preaching about evil ways of Western capitalism still reek of Lonely Planet's self-appointed role of bettering the world. Quite annoying, really, and in many cases hypocritical, coming from a lean-and-mean profit-making publishing house.
Most facts about travel, eating, accommodation, etc are accurate and well-researched, although as usual information to someone with a bit bigger budget is very fragmented.
They could give more information about useful websites for both ticket booking and accommodation.
Overall, if you are only buying one book for West Africa, this is the one. If you can get two - buy the Rough Guide as well: it may be boring and cultural information reads as if it was written by your local tax office, but you will get many additional addresses and phone numbers.