I like it. I'm a big Abnett fan, so really looking forward to another novel from him. I love the HH series, so you know I'll be buying this anyway. I even think the artwork is cool. In the fluff in days gone by GW have mentioned Space Marines fighting at the bottom of oceans and in hard vacuum time and again, but as far as I can remember, this is the first time we have actually seen it in artwork (please someone correct me if it's just something I've not spotted in the last 14 years).
Not sure how I feel about Gulliman going helmetless in space, but then again if anyone could it would be a Primach. Equally, if I can suspend disbelief enough to accept tat Imperial aircraft could actually fly, I'm sure I can cope with this