Finished reading both parts of "Hollow" and I won't add too much to AJK's excellent overview of the first part...except that the Senator could be someone whom is very close to Clark, and whom we haven't seen in a while, since the series concluded, and explain why Superman is in Washington. I have a feeling that Diana will be working through some Themiscryian Embassy. It was also nice to see Dianah and Mia. Q showing us that Watchtower does indeed have agents operating across the globe. Really though the core part of the story is Tess's struggles with adjusting to her new life as a digital construct/avatar.
The second part focuses on Lex...Timm'Verse fans will recognize Angela Chen as the reporter on scene. So again Q is giving us little treats and Easter Eggs along the way. Lex has discovered the Earth 2 ship that Chloe and Ollie discovered way back in "Guardian" and wants to acquire it. So once again things are moving along quite nicely.