The title of Dark Moon refers to its authors' claim that, according to their interpretation of the Apollo 13 timeline, had the ship continued uninjured it would have arrived at the Moon too soon, and that its landing site would have been in darkness. This, they say, proves that Apollo 13 was planned from the start to be a staged failure. What they don't realize is that upon arrival at the Moon, the Apollo spaceship nominally goes into a ten-revolution calibration orbit, at two hours per rev. That's to allow ground controllers to observe the orbit and finely measure it, so that the descent maneuver can be planned.
That's only one of perhaps a hundred important elements of space science and engineering the books authors are completely ignorant about. Neither one of them is a space scientist or engineer, and there is practically no end to the stuff they get wrong.
One of its authors, David Percy, is a photographer and purports to have proven by photographic analysis that the photographs can't have been taken on the Moon. Unfortunately he has no skill or talent at photo analysis, and this should have been made apparent to him by the responses he got when he first published his claims in the Fortean Times. Instead of reconsidering his approach, he seems to have been encouraged, and so wrote one of the longest, most meandering books on any fringe subject I've ever seen. Plus he went on to make a four-hour video, excerpts from which can still be found on YouTube. (He's the bearded, congenial English fellow).
I'm not speaking acerbically when I opine that the vast length of his material is meant to lull the reader and viewer into a stupor from which he finds it difficult to think critically.
Percy attempted to defend his photo analysis, but broke off sharply when an astute reader pointed out that his own photographs failed the "tests" Percy proposed had to apply to real photographs. In other words, Percy simply makes up what he thinks is the science of photo analysis and interpretation, doesn't test his methods, and then runs away when reality intrudes. In the meantime all the rest of his claims have been fact-checked and found to be sadly wanting. Good luck getting Percy to discuss his work in public anymore.