When I started this book I really enjoyed what I was reading - it struck me as being what the Da Vinci Code could have been like with a competent author at the helm. That feeling lasted until about half-way through, when the plot suddenly degenerated into a kind of pseudo-science-fiction mish-mash which was completely unbelievable on all levels - no matter what your personal feelings about parallel universes or multiverses. I persevered for another couple of chapters, and then gave up. I simply couldn't be bothered to finish it.
That said, the author's writing is excellent, with good characterisation, crisp dialogue and formidable descriptive powers. If only she could devise a sensible plot ...