Red Hood: The Lost Days is a cohesive stand alone story that also adds and expands on Jason Todd's transition from death to his identity as the Red Hood.
The writing works really well, both in creating single issues that function themselves and towards a cohesive whole. There is a good balance of exploring emotion as well as action, and where I often feel that having a character continually narrate in a comic can at best explain the obvious, I found the narration worked really well as it sounded like a distinct character was talking, instead of a writer fretting that the reader hasn't put together all the parts.
What's better, I found myself genuinely sympathizing with Jason. I hated Batman when it was shown that he had taken on Tim Drake as the next Robin, and my heart went out to Jason when he discovered that the Joker was still alive. I noticed a lot that in close up panels with Jason, there would be no light to his eyes; whether that was intentional or accidental, it really helped to subtly illustrate how broken Jason was feeling.
The art definitely picks up with the second artist, though I found both fell into the trap of using the same drawn image repeatedly with slight modifications (cropping, close ups, showing pauses, etc). That said, the colors and strong inks do a lot to get across a rawness to the book, which fits Jason and also Talia's emotional states. The panel flow works as I never felt jarred or confused about how to read the page, and I found Jason's physical growth from teenager to a twenty-something believable—he's fit, muscular but without too much bulk (all the better considering how much of an acrobat he was and continues to be). That said whoever did the issue covers really should have been replaced as the colors, imagery and physical depiction of Jason Todd/Red Hood were completely at odds from the tone and look of The Lost Day's content.
I'm sure some people might have reservations about reading a book where a former Robin turns into a calculating, vengeful killer, but honestly, when the past involves taking a child and arming him with martial art techniques, weapons and technology, and when that child's mentor and father figure portrays himself and the child as dispensers of justice, above the law and all reproach, where physical violence (often extreme physical violence) is almost always the solution, the shocking thing to me is not that one of the Robins went rogue and took combating crime to its logical conclusion. What surprises me is that it took a death and rebirth to get there, and if the Batman mythos wasn't so completely entrenched with regard to no killing, I'm sure DC would have gone in that direction ages ago.
*ultimately the Batman/Robin dynamic and mythos is utterly creepy when you think of a filthy rich bachelor millionaire taking in children, raising them to risk their lives each and every day while building a freaky one-sided codependent relationship. It's remarkable that the tabloids aren't accusing Bruce Wayne of being a pedophile, let alone putting two and two together but maybe that's just me.