I haven 't read Mike Brotherton - he has a blog at www.mikebrotherton.com
- but he writes 'hard as nails' sf. His first novel can be downloaded free at his website as a promo for the new one.
You might want to try Iain Banks' Culture books, particularly 'use of weapons'.
I'm not a huge fan of Bova, but I enjoyed 'Voyagers'.
Robert Forward's Dragon's Egg is another 'hard as nails' novel.
I don't like 'high fantasy' either, but I'd still recommend Robert Holdstock's Mythago Wood, which is a science-fictional approach to mythology as a construct of the collective conscious of humanity but projected onto the real world.
I don't know, by the way, if all of these are available as ebooks - you'll know once you input them at fictionwise, etc. But I also have a sony, and know for a fact several of Alistair Reynold's books are available there.
If i were you, I'd check out Linda Nagata's 'Vast', which may or may not be an ebook.