I really enjoyed the concept of this book, and most of the execution too. I did think it was too bad that in the summary on the back of the book the main character was referred to with the 'he' pronoun, while the book makes it very clear that that is not the case. It easily could have been replaced by 'they' and thus avoided influencing the first impression of the character this way.
(I guess it may have been a deliberate choice to maybe make you look at how first impressions influence you and how it can be difficult to step away from them, which is also a theme in the book I guess, but I would have preferred it not be that way.)
I also could have done without the chapter full of fatshaming.

I also thought A was being rather stalkerish in the beginning, and that his obsession with Rhiannon was a bit creepy. Then again, when you are in a different body each day, with new people around you each day, maybe it makes some sort of sense when you have a really good click with someone, that you want to stick around for once, have someone get to know you, etcetera.
I in general have a bit of a problem with these 'instantly obsessively in love' situations, so that doesn't help, probably. Ah well.