For those of you that are new to this kind of material, then it's a must have. Firstly, Farrell is readable - a mix of the technical and formal, balanced with a clear, descriptive style. He covers a lot of ground (from Sumeria to America, the Annunaki to mitochondrial DNA....) and does so in enough depth to whet your appetite, but not so much you're left puzzling over the meanings.
For those that have read this kind of thing before (Sitchin etc.) then you may be pleasantly surprised at the range of material in here. I certainly had not come across some ideas/sections before. For example: the Sirrush. The book opens with this strange creature and it's certainly an intriguing read!
The reason I've only given it 4 stars is twofold. Firstly, some sections plant some great ideas but fail to dig deep or do anything more then scratch the surface. This is a shame but you could follow up lines of investigation with other authors/works if you felt so inclined.
The second and reason is serious. For someone as clearly intelligent and well-read as Farrell, quite why he insists on quoting from Wikipedia beats me. Even the kids I teach know not to use Wikipedia due to its unreliability and high rate of error! It doesn't just happen once - but he makes numerous references to it throughout. This is inexcusable. When you're researching and promoting 'alternative' theories, you're evidence has to be airtight. Using Wikipedia to prove his ideas undermines all the hard graft Farrell does everywhere else.
Added to this, he also spends a great deal of time quoting from Knight and Butler. This was fine until I realised these were the two authors behind the god-awful 'Who Built the Moon'. My estimation went down at this point. (You can read my review of that book to get the idea of my feelings about it!)
However, if you're prepared to dig deeper yourself and can overlook the use of Wikipedia, it's certainly worth a look.