You will always have errors doesn't matter if they are local or not. The question is whether it is a good (generally accurate guide) or bad. Has a local done a guide? Is it better than the non-locals book? Either way buy the best book unless the local has done a lot more for the area and you really want to support them financially.
I agree with Christian's comment. And beyond that, the content choice and layout/design of the guide does nothing to celebrate the tradition of Needles climbing- I feel it's more of a mockery, although I'm sure that was not the intent.
A decent effort, but nowhere near being THE guide to the Needles. For this, we still wait...