This book is a hodge-podge. It opens with Osborn inspecting Taskmaster's Camp HAMMER training facility. It's at this point that Osborn surprises him with an invitation to join the Cabal. He knows that's over his head but doesn't see another option. He's out to survive Siege with his own skin intact. And he tells the reader that REPEATEDLY. In fact, his running internal monologue began to wear on my nerves because it was so boring. It's through Taskmasker that we meet Constrictor and Diamondback. She's a mole for the real Avengers (though not the usual Thor, Cap, etc. Avengers), which doesn't stop her from having an affair with Constrictor. Her constant inner monologue questions how she feels about him; he loves her, but she used to be involved with Steve Rogers, a real hero. I AM NOT MAKING THIS UP! Then we have a team of Avengers in hiding composed of lesser-known heroes like Tigra, Night Thrasher and Justice. When Osborn becomes distracted by the main Siege battle, they decide to help their hero friends by attacking...Camp HAMMER. Because that is a critical target? It just didn't make sense.
And then the last quarter of the book is taken up with a couple of random adventures of some of the Initiative "heroes" - characters I have never heard of - that had nothing whatsoever to do with Siege. Two-gun Kid? Really? Amidst these stories we have Komodo and Hardball, whose relationship is broken when she learns he's an unwilling Hydra operative. It felt like I was reading bad teen fiction, there was so much angst.
Overall, this was a complete miss for me as a Siege tie-in. It doesn't provide any additional perspective on Siege, unless you count Taskmasker's, and it is filled with so much personal relationship-angst that it strained credibility. There are a couple of memorable scenes, so I gave it two stars. But, sadly, I just can't recommend this.