A promising adventure crushed by a suffocating romance. 3/5 stars. 
 This review was originally posted on my book blog. 
 This is a story of two parts. One part is a fantastical time-travel adventure motivated by a centuries-old family feud. This layer of the story is wonderful and takes in a range of locations and time periods, each described in evocative detail. 
 The other part of the story is a romance. One which starts when the two characters lay eyes on each other and pretty much fall in love in that second. And from then on the romance grows until it overshadows and sucks the life out of the adventure plot-strand. As someone who loves a good love story, I say that with a heavy heart. But when there are whole chapters or great chunks of chapters which are devoted to the two main characters thinking about each other and their feelings, rather than actually doing anything... I lost patience. 
 The characters are a laudably diverse cast who are brave, determined and smart. But while I liked the two main characters - Etta and Nicholas - I felt their personalities failed to flourish because their feelings for each other (so many many feelings, told again and again and again) overwhelmed their individuality. I think the whole book would have benefitted if they had started out as companions who are rightfully wary of each other and then their relationship had been allowed to develop into a romantic one while the adventure stayed in the front seat. 
 I would like to read book 2 because if the romance were dialled back, there's potential for this to be a fantastic series. The time-travel element is well-handled and I'd like to see where and when the characters will be taken next. 
 Overall: if you can't stand insta-love, you might want to avoid Passenger. However, if it doesn't bother you and you're looking for a well-written time-travel adventure, check it out. 
 Thank you to Hachette, Quercus and Netgalley for giving me an e-copy of Passenger in return for an honest review.