Fallen Angel the series is great. It features interesting characters, deals with grown-up situations (I'd say "adult" situations, but "adult" has the wrong connotation here), and asks hard questions. This series pulls no punches: the Angel isn't afraid to do what she feels she must, but she's not perfect and does make mistakes. Combine that with some interesting religious ideas, and you've got a gem of a series that DC Comics just did not know what to do with. It has since found its home at IDW Comics.
This edition is the first collection to feature all twenty issues of the DC run, which is a precursor to the current IDW series. If you've read the IDW stuff, then this will inform and enrich your reading. If you haven't read the IDW stuff, this is a great place to start: same author, same basic cast, same setting. Think of this single book as "Fallen Angel: Season One" and you've got the idea.
The only reason I've rated this 4 instead of 5 stars is because of the slightly smaller size of the book when compared to the typical "trade paperback" or "graphic novel," which is generally sized like a typical comic book in height and width. This copy is comparable to the Dark Horse Omnibuses that one sees for Buffy or Star Wars. I'd rather see David Lopez's art on a larger page.
However, as this is the ONLY collection of this fantastic run of comics (a run with big pay-offs in the later IDW series) and it's VERY inexpensive (20 comics for $22, which is ridiculously cheap) while still having excellent printing and paper, you can't go wrong with this title. Highly recommended to fans of comics for grown-ups (Fables, Preacher, Y the Last Man, Sandman, etc.).