Just finished reading these in TPB. I've read the single issues several times but I must admit that on the whole the story plays a lot better without ads and chapter breaks.
I remember reading it as it came out monthly, and to be honest it was a bit hard to get into that way. The way the story reveals itself in layers with the reader only being given the full picture right before the end makes it a lot of fun to read all at once, but in bits and pieces with a full month in between each chapter it was a very divisive piece of work at the time it was first published.
That was during the time when each of the three Superman books was given its own writer and independent storyline that would ostensibly last for a full year - Azzarello on "Superman", Greg Rucka on "Adventures of Superman", and Chuck Austen on "Action Comics" - as a way to refocus the Superman books and get things back on track after what had previously been a very rough period for the character across the board. Most of the Superman books published between 2002-2004 were "uneven" and inconsistent, to be perfectly kind, and some of them were downright awful. So the "new era" that was set to cover 2004-2005 was designed to simplify things and give people a new jumping-on point.
Unfortunately, that didn't really work out as well as it was hoped, especially since Austin's run on Action was so dreadful, he was kicked off of his own story before it finished. Rucka's run on AoS was much more well-received, being a rather straightforward Superman story, very well-written even if not altogether groundbreaking. And then "For Tomorrow" was somewhere in the middle, for most people. Everyone agreed that the art was fantastic, but not everyone liked the slow-burn,
in media res storytelling and were hungry for something more conventional and straightforward. Again, the Superman books were coming off of a REALLY bad slump, and for the most part people were desperate for something more "back-to-basics" than what this story ended up being.
I do very firmly believe that the timing of the project had an unfair effect on the overall perception of the work at the time it was being published. In a vacuum, reading it as its own stand-alone piece of work, all in one sitting, I feel that it's quite brilliant. In 2004-5, though, it was a bit of a hard nut for many people to crack. One thing I remember vividly was everyone getting very hung up on the continuity of it all, where it "fit" within the other DC and Superman comics that were in print at the same time, and they were letting those concerns affect their ability to take the story on its own terms. Now, to be clear, this story IS in-continuity - much of the unresolved plot threads were directly planting seeds for "The OMAC Project" which came out shortly thereafter - but nobody reading it had any way of knowing that at the time, and since AoS and Action made no reference to the events of this story at all, some people were quick to dismiss it simply because there wasn't more obvious connective tissue to the other Superman books. I'm on-record as being a huge fan of continuity, but at the same time it can very often hurt the ability to enjoy a story on its own merits if you spend
too much time thinking about where it fits with other, unrelated stories. And I do believe that's what initially happened with this one. Between the "Where does it fit?" questions, and the fact that the story often jumps seamlessly between flashbacks and present-day scenes without much transition, along with the fact that most of it isn't fully explained until the very end of the story, reception to this one was VERY mixed during its initial run.
That said, when taken on its own and read in a single sitting, I feel that all of those issues evaporate, and what you're left with is simply a really great Superman story, one that deals powerfully with themes such as Hope and Faith, Superman's constant internal struggle between doing "Too Much" and "Not Enough", and how far he's ultimately willing to go to "save the world".
It didn't much hook me as a monthly read, but since then it's easily become one of my all-time favorite Superman stories, and it's one that I feel still often gets unfairly overlooked. It's great.
Huge Recommendation.