Al Ewing and Pepe Larraz deliver a smaller stand alone story about three Avengers trying to help people affected by the Terrigen Mist in "Avengers Assemble" #20. The book is solid, but unmemorable.
Ewing's story is clear in its goals -- a small done-in-one -- and it's successful in that endeavor, even though it's inconsequential to any larger whole. Though there are some cloying and cliche elements (parents of a missing/dead child, a child in jeopardy, etc.) Ewing does his best not to dwell on those things. In the case of the child in jeopardy, he actually manages to not only resolve that nicely, but throw in a bit of fun in how it resolves it and both things are much appreciated.
The book is adequate but there's simply no meat here. The story is as inconsequential as could be. The characters lives at stake are four strangers that it's impossible for readers to connect to, and three Avengers that never feel in any real danger given the brisk pace needed to finish up the story in a single issue. There's also not enough time for much character development or emotional resonance. There are some fun lines, and the argument between The Wasp and Wonder Man on the Quinjet (with The Scarlet Witch amusingly refusing to get involved) is certainly the highlight of the issue since we do actually care about those characters.
Larraz's art is solid and occasionally exceptional, but it's a little inconsistent. He illustrates Wanda, Janet and Simon, as well as all the more superheroic stuff wonderfully, but the more mundane "life stuff" is less impressive. A double page spread of superhero action (and arguing) followed by a full splash page of a giant naked non-superhero man walking down a street are magnificent, but other pages are less successful and rougher around the edges in every way. That said, the storytelling is always clear and easy to follow, and that, combined with those few bright spots, makes the art satisfactory on the whole.
In the end, there's just not that much to get excited about or connect to within "Avengers Assemble" #20. The comic itself is fine, delivering a clear and easily understood story, but it's not one you're likely to remember and at the current price of comics, adequate but unmemorable is just not enough.