Well my good sir you are in luck.
There best CD that has the most well rounded sound that's appealing to most folks is Aenima. It doesn't have a bad track on it IMHO, they are all wonderful. Usually I try to say listen to this album first because it's the best album to get a feel for what Tool is capable of doing. You probably don't care for 10,000 Days because a lot of the album is slow and melow. Vicarious, Jambi, Right in Two, and The pot are the easiest songs on that album to like. wings for marie part 1 and 2 are wonderful it's just you may not like it at first.
Opiate and Undertow are albums that are the earlier stages of Tool and show a more harder rock/aggressive side of Tool. Undertow you for sure need to check out all of the songs because they are all great IMHO. Especially Flood. That's a treat to catch if you ever get to see them live. I don't believe they've played that one in a while.
Lateralus is a beautiful album because it has The Grudge, The Patient, Schism, Lateralus, Parabol, and Parabola.
Salival is a live album they did which has a wonderful version of third eye and Pushit. Pushit is by far my favorite song by Tool and the Salival version just takes a wonderful song to another level by showing a softer, easier side to a harsh and aggressive song.
I hope that gives you a better understanding of the albums. Ask anyone here, I always love to discuss Tool/APC //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif