Just One Day is well-written. Immensely well-written. If you pick this book up, you'll definitely get hours of entertainment. However, the plot line is lacking from the get go. This trilogy really could have been just one novel.
The best thing about the entire trilogy for me was the locations. This one book is mainly set in Paris, but through the three we get to see a lot of Europe as well as the US. Trips through hostels and train rides feel very real and are a great way for us to experience the world through a book. The setting feels real, and though the premise isn't very likely, Forman convinces us that this could happen to you tomorrow.
The romance between the two main characters feels very real, but when you pause to think about it, doesn't make any sense. Allyson, our main character, is very relatable. We can all feel like we've been in her shoes. However, as a character she doesn't stand up very much, and at times we want to slap her for the decisions she's making. The two main characters really don't have many commonalities between them.
This entire book follows the course of two or three days, and in these days, Allyson makes several out of character decisions. While these move the plot along, they don't really fit in, and I'm appalled that her friend let her make them. At the same time, we are living vicariously through her and in a way she's living vicariously through herself--and will later through her memories--so in a meta way, we relate to her even more.
I really enjoyed this book while I was reading it, but when I stepped back, I was left wondering what I'd just spent my time on. The sequels were available at my library so I read them, but I by no means felt compelled to.