First, if you bought The Long Earth because Terry Pratchett wrote it, know that it is absolutely not the style or type of a Discworld book. The book probably should have had Stephen Baxter’s name lead because my understanding is that he’s a “hard sci fi” guy and while this isn’t the hardest of sci-fis, it’s definitely not fantasy.
Second, the writing is solid, the plot is credible and creative, and the ending is a gut punch, in just the right way (especially as the first book of a five book series). There are a few dead spots where things get a bit monotonous but it’s also easy to argue that the authors were trying to let you know that it felt monotonous to the characters too.
And there is a main character that I’d gladly punt out a window, but I suspect that’s also intentional.
There’s no romance (thought I can’t say for sure that some won’t develop in a future book) and a lot of good common sense thinking from the main characters. There’s only one spot where you’ll be yelling “don’t do it!” at the book, which is good. The biology elements are awesome, as is the geography and geology. And the “magic” is consistently applied, so no giant plot holes.
I’ve already bought book two, and I suspect that I’ll be reading the entire series.