The first Animal Man volume serves more as an introduction to the character than as an actual forward-moving storyline; if you're looking for a complete story when you read the first trade, then essentially you've signed on for all three volumes. This kind of "collection of issues" storytelling caught me off guard, frankly, until I realized this used to be the norm, spoiled as I've been by our new era of books written for trade.
The first four chapters (which, author Grant Morrison notes in his introduction, he originally wrote as an Animal Man miniseries) pit Animal Man Buddy Baker against B'Wana Beast, with Animal Man reluctantly on the side of STAR Labs animal testing division. The fifth chapter is a self-contained story that introduces some of the ongoing existential themes of the series; the last four chapters take Buddy Baker in and out of DC's Invasion mini-series. In this way, we get an enjoyable introduction to Buddy and his family, spend time with them and learn some of their foibles, but the last two chapters contain quite a bit of foreshadowing that won't be resolved until future trades.
Morrison, as is appropriate, uses much of the story of Animal Man to turn around the lens and focus on the beastliness of man. In the first four issues, B'Wana Beast shares true love with his gorilla friend and a cat gives her life to protect her kittens, while scientists torture helpless monkeys and hunters threaten rape against Buddy's wife, Ellen. The parallel storytelling here is genuine though arguably heavy-handed, but Morrison makes up for it in the second half of the trade, where the suggested existence of a higher power puts to lie the idea that mankind is the dominant species. As Morrison's ideas become more complicated, the book benefits overall.
There's lots of blood in Animal Man, and while there's no real gore per se, reading this trade gives an interesting hint as to the evolution of the Vertigo comics line. Though Grant Morrison left Animal Man before it joined Vertigo, the end of the first storyline where an scientist gets his comeuppance us reminiscent of the kind of psychological horror later found in Sandman.
I read Animal Man in part trying to understand certain scenes in DC's 52, without much luck. Indeed, Animal Man starts well after Buddy has received and learned about his powers; this makes the trade no less enjoyable, but don't expect to come here and find lots of DC Universe continuity (short of a spot-on cameo by Martian Manhunter). Should more appear in later volumes, I'll let you know.
[Contains full covers, introduction by Grant Morrison.]
A review of the second Animal Man collection coming later this week!