As a fan and follower of the X-Men and as interested as I was in the Siege event, as soon as I saw this book at Amazon.co.uk I immediately decided to buy it. The first and most important thing I must say about this is that Siege: X-Men doesn't speak of the X-Men at all, as they didn't participate in the siege. It concentrates on the events around two mutants, Daken and Valkyrie.
I know little of Daken, having seen him only a few times and having never read anything on him as main character, so I felt a bit lost while reading this comic. I do agree that the story was well adapted to an Asgard focused moment in the Marvel history, but other than that, I didn't connect with Daken and couldn't really follow his behaviour. This might have been intended, but because I know very little of Daken's personality, it just made me feel less interested. The story itself ends with a loose end making me recommend this only for people who already read or intend to start reading Daken.
Valkyrie's story was somewhat more interesting to me. Although I also know very little of her, this is a well written and well closed short story and I liked following Valkyrie and Hela's interaction. Niko Henrichon's illustration adds a lot to it, both the drawing and the colouring are amazing.
The last part of this collection is Siege: Storming Asgard - Heroes and Villains which is H.A.M.M.E.R.'s collection of information and analysis of almost anyone with some importance for the Siege event. I did enjoy going through this as trying to get inside Norman's mind (though not too much for the sake of my sanity) as he plotted the destruction of Asgard as a definitive step on to becoming leader of the United States and then, probably, of the whole world.
Overall, Siege: X-Men was OK but not actually worth buying as a hard cover, one might as well read the individual comics and I suggest the collection only for readers that follow Daken and Valkyrie specifically.
I'm trying to write quick comments about all the books I read in the last month as I won't have time to write proper reviews but I also don't want to bypass them all. I'll write a comment on the next comic as soon as I can.