I read this book not long after reviewing 'Gemini' and, for me, it is a much better novel, well worth the four stars.
In 'Gemini', there was so much confusion whether Petra Reuter would ever disappear and revert to Stephanie Patrick and now in this book, despite the title, several more identities crop up, disappear, reappear until, finally, there is a meeting with an active lookalike. Still all very confusing for the reader but, thankfully, it does pan out and gradually become clearer.
There is plenty of action, just a few pages of the author's view of life which I could do without in the scheme of things. However, as Stephanie does do a sort of 39 Steps journey across continents, the body count rises inevitably, often in a gruesome way as she finally manages to track down who has set her up for a big fall. Again, in keeping with 'The 39 Steps' she has a reluctant helper in tow whose role in it all does appear a bit iffy and is never really fully explained as to why the bad guys fear his contribution so much. Anyway, thanks to his brief stint of training by a Finnish Rally Driver, he does save the day at one point - yes, you can suspend disbelief and move on.
The pace is good, rather too much dialogue for my taste but all-in-all, a big and more entertaining improvement on the earlier novel (I haven't read the first two). I don't know if there's fifth in prospect but the door is certainly open and I would certainly buy the book if so.