If you're looking for a sappy romance - this is not it. If you're looking for a book that contains two rough men fighting through the enemy's territory, running for their lives - this is it!
What I love about 18% Gray is how naturally the "romance" develops between the two guys. The bits where they did connect on their journey were touching and heartfelt without being overly so. I loved the beginning, so funny. I also admire the way Anne Tenino writes; fluent and clever.
The name of the book is great, but other than a very brief mention of 18% gray, I really don't see the relevance. Except maybe that the gays in the Red zone have to hide and use symbols to get lucky.
I also don't see the purpose of Benigna, unless she has something to do with the other books. The one part I can see her moving the plot along (after the brush incident) would have been solvable without her. I don't know if she was for comic relief. The little "nunette (love that word) frustrated me more than anything else..
There's obviously going to be a second book and I can't wait to read it :)
Definitely 5 out of 5 - heck, make it 10 out of 10!