This was a pretty interesting story by itself, when taken apart from the rest of the Sandman series (which I had to do by default), with some very interesting themes about mistakes, consequences (even, or perhaps especially, from actions with the best of intentions), regrets, asking for help, reality, and family relationships.
As with other graphic novels, my biggest problem was that often I couldn't figure out the direction to read things in (this was not consistent from page to page) and I'm only mostly certain that I understood what was happening. But it was interesting, and the artwork was really beautiful. Perhaps not the best place to start in the series, but it certainly didn't put me off reading the rest of the series, and I think worth reading for its own merits. After #1-75.
Keep reading! Beth
*The funny thing was, several times in the book Gaiman specifically says that this is not a good place to start for new readers of the series, but I was already committed so I persevered and, feeling very rebellious, completely ignored the author's own warnings. This was perhaps a mistake, as I did think the Overture was a little strange, but on the other hand, was a pretty cool introduction to the series. But maybe don't follow my lead :)