This book was terrible. I got a little less than half way through before giving up. The prose was obviously intended for a very young audience in a way that has no appeal to anyone over the age of maybe 12. The juvenile narrative and dialogue was written in such a way that there was an overtly implied *wink wink* at the end of every chapter that gave way to the predictable events that followed.
The main characters, the twins Sophie and Josh, are in no way compelling or well developed. Their dialogue is amateurishly written and doesn't resemble anything actually teenagers would say. The attempts at character development contain incoherent pop-culture references by an author clearly much older and out of touch with the character's he has written. The authors apparent out-of-touch approach to writing and developing young characters makes the time frame almost indistinguishable (an "average 15 year old boy" would not simultaneously reference Shrek/first person-shooters and Penn and Teller). The over-use of modern day technology is also heavy handed, with unrealistic usage and references to email, google and wikipedia that again in no way resembles realistic modern teenage dialogue.
The structure of the novel is also skewed in a way that takes from plot and character development. Instead of a natural growth of character to main plot to development of world(as expected in a fantasy series), the novel immediately throws into the action and conflict giving no idea of the characters or any indication of the fantastical world in which they live. Attempts at character and world development along with backstory are awkwardly thrown in to convenience plot progression, then reiterated several times (Josh likes video games! Their parent's are archaeologists!)
The plot and story itself contain much potential, and at the hands of a better author could have been the beginning of another young adult fantasy series.