Book three of the Expanse series is Abaddon's Gate.
Abaddon's Gate starts out as a continuation of books one and two.
Which is great, and I would have been just fine with that.
But then, about halfway through (page 266, to be exact), Abaddon's Gate takes a sudden and startling 90 degree turn, revealing that much of what you thought you knew from the first two books is completely wrong, and exposing a whole new set of ideas to contemplate.
And so, then, off we go, in a completely new direction!
One of the things I'm really enjoying about the series is the "long now" perspective that it takes. You might think that a couple thousand years of written history is a pretty decent accomplishment for a sentient species, but pah! that's really nothing, in the big picture of things.
If you liked the first two books, you'll enjoy Abaddon's Gate. If you didn't like any of this, well, you probably figured that out about 50 pages into Leviathan Wakes and that's fine, too.