I agree with most of the above.
JMHO, the UG has some good information about hotels and DLR restaurants.
But I did not find their descriptions of the DL and DCA attractions to be useful. In fact, I found them to be harmful.
I think the descriptions were written by a "worry wart." The descriptions have too many worries, concerns, and complaints--you would think that they were preparing us to climb Mount Everest.
Also, their descriptions of the attractions are loaded with spoilers. I would skip those chapters, and instead go to
www.wdwinfo.com and click on the Disneyland tab and then click on "Theme Parks" (or you can go to the top of this thread and click on "DL Theme Parks"). I think the level of information about the attractions that you will find there is much better than the UG.
I found the touring plans in The Unofficial Guide to be "commando," but that's just my opinion. You might want to find out about Ridemax.com, which the Unofficial Guide conveniently never mentions.
I think the Birnbaum's Guide is helpful. But like bumbershoot wrote, you might be better off borrowing it from the library (the same goes for the UG).
But what's so great about books?
I agree with the Hound -- check out HydroGuy's sticky near the top of this discussion board ("HydroGuy Tips Compilation"). In many ways, HydroGuy's information about Fastpasses, touring strategies, etc. will be much more helpful than the UG.
HTH.