First off, the usual disclaimer: I believe Greg Egan to be the absolute apex in the "science" chain of hard science fiction - his ideas are always one (or a dozen) steps ahead of anything I've read by any other author, and his world-building is stunning.
"Dichronauts" is no exception: choosing to set a novel in a universe with very different rules from our own is a long and respected tradition but the care and depth of analysis you'll find here is not as common. Of course, since it's not a treatise but a novel, Egan had to take some (several) shortcuts - the protagonists are explicitly tasked to explore and explain their world, which leads to more pages of exposition than I'd probably like, and there are occasions when their inner monologue (or conversation) have a slightly off-putting "As you know, Bob" tone. On the other hand, without information like this the reader would have to spend half the time consulting Egan's webpage to understand what's going on, so I feel the tradeoff is more than justified. As a side note: I strongly recommend doing that anyway, because the images and animations in the site's section dedicated to "Dichronauts" are rather useful for those of us who cannot easily visualize the consequences of having two time-like dimensions.
From a "literary" standpoint, the style is pretty much what readers of Egan are used to - clear, succinct prose with very few unneeded sentences - so I would say that appreciating his previous work is a rather solid indicator of whether you'll like this one. The converse is also true, unfortunately: if you don't like his pragmatic approach to character development, or his tendency to veer off into scientific discourse when you least expect it, you probably won't like this.
One final note: in more than one page it's easy to read between the lines and find socio-political commentary on the issues and subjects that Egan has explored in the past: (im)migration, reaction to and acceptance of different cultures, self and personality and so on. Given the colossal differences between "Dichronauts"' universe and ours, though, it's rather hard to understand when that's a deliberate choice by the author and when it's just me projecting.
In other words, while it's tempting to read "Dichronauts" as a super-charged Flatland, I feel like that would be doing a disservice to both: reading it as a stunningly in-depth documentary set in a majestically ambitious thought experiment is probably the right choice.