Adventures in Wild Space had stayed in its predictable formula for the past few entries, and The Darkness (or The Dark, depending on which edition you have) shakes it up a bit -- although it's not all positive. If you've been following the series to this point, there's no reason to stop now; but if you haven't been compelled to start reading yet, The Darkness doesn't make it more enticing.
The Darkness shakes up the status quo a bit for child protagonists Milo and Lina Graf. They're still on the trail of their parents (and they're still making progress toward that goal at a snail's pace, seemingly to draw out the series as long as possible) but now they're in the clutches of a devious bounty hunter. They stay that way for much of these ten brief chapters and the resulting tale is much more, well, dark as a result. Kids are locked up, stun batons are used, there's (sort of) a killer on the loose, there are mechanical spiders crawling all over the place, and at one point the lights go out. It's slightly horror-tinged, although it's still a kids story so it's not really that scary. If your kid is deeply afraid of spiders though, you have been warned.
All this is well and good, and it makes for a brisk and entertaining tale. But it doesn't really go anywhere and, as always in this series, we end almost exactly where we begin: The minor conflict in the book has been resolved, and the kids are on the trail of their parents once again. The annoying logic of Milo and Lina is also amplified in a lazy way here. I was impressed that they both seemed self-aware at having made naïve decisions in previous novels and were resigned to do better, but then they make an even stupider and more obviously terrible decision shortly afterward -- probably the dumbest thing they've done in the whole series so far in a very clearly contrived scenario designed to set up a twist that anyone could easily see coming.
So as always, you know what you're getting with the Adventures in Wild Space series: A basically reasonable and entertaining Star Wars kids chapter book that is one tiny step on a very slow-moving journey with a little bit of dumb kid logic thrown in for good measure. Good for what it is, I suppose.