I was trying to know the ending of the stroy after starting The TV show, and I picked up the book. The design of the story was good, but the use of language was not pretty. The author was just trying to show the plot and didn't spend enough energy to build the characters
Writing my review in English because my Chinese is only good enough for reading. (Heh.)
I happened to watch the drama first, then decided to check out the original novel. So I may be biased, but I think the drama does a better job fleshing out the secondary characters who were on the bus. Here, they don't stand out as much, and they aren't as endearing. The drama also has certain tweaks that make both the protagonists and antagonists more sympathetic. So I prefer it, although this book is still interesting.
Got to the end of the main story, then laughed as I realised the first bonus chapter is a whole-ass novella about a delivery man caught in his own time loop, desperately trying to deliver a secondhand camera lens to Xiao Heyun. The man's name is 宋卜道 (Song Budao), which is a blatant pun on 送不到 ("cannot deliver"). The sheer hilarity.
It is not identical to the series, and by the end of the main story (the bus plot) there were a few significant deviations. However, the essence of the story remains the same, and makes for an interesting read even if you have already watched the series beforehand. One benefit of reading the book is that it explains in detail some things that would be unnatural to explain in the series (like why the bus is more empty) and also includes some elements that I felt did not come through as well in the series (the bus driver's fondness for 诗情).
While some people feel that the characters were not as well fleshed out as the series, I think that it is not that evident if you read the book independent of the series. Adding too much background to the secondary characters, on the other hand, runs the risk of making the story draggy. The addition of such backgrounds was very well done in the series, but I don't think that it makes the book any weaker.
I did not read the second part of the book (送不到) about the delivery driver, as I was unable to overcome my general aversion to second person POV.
I would recommend this book even if you've already watched the series. It's not exactly the same, but that's also what makes it fun to read.