If you can effectively manage your time so you don't become an addict, you should definitely get WoW.
Gameplay:
WoW is your typical MMORPG. The first thing you must do is choose your realm (server). There are several types of realms: PvP (in most areas players of oppossing factions can freely attack each other; this is the more "hardcore" of the realm types), Normal (also known as PvE; players cannot attack each other unless in battleground instances or if they choose to flag themselves for pvp combat), RP (roleplaying, essentially a normal server in which players choose to act out their gameplay through role-playing dialogue; there is no actual difference between RP servers and other servers aside from teh fact that you can get reported for breaking character sometimes), and RPPVP (Roleplaying Player versus Player; essentially just a RP and PVP server mixed). Once you choose your realm, you create a character based on eight (ten in the upcomming expansion) races over two factions. You can be part of the Alliance (Humans, Dwarves, Night Elves, and Gnomes-including the Draenei in the expansion) or the Horde (Orcs, Tauren, Trolls, and Undead Forsaken-including the Blood Elves in the expansion); you can also change various visual aspects of your character including age, hair color, skin color, and accessories. Once you create your character, as wtih any MMORPG, your main focus is on leveling. Your character starts at level 1 and can level up to 60 (increased to 70 in the upcomming expansion). If you devote all of your free time to the game, or if you just know how to level up effectively, this 1-60 span can take about two to three months (supposedly getting to 70 from 60 in the expansion will be as hard as getting to 60 from 1). You level up by earning experience points. You earn XP by killing monsters and completing quests. There are also various professions and skills that your character can learn in order to make money/items or just for fun. This is an MMORPG, so socializing is a huge part of it. You won't go through WoW without grouping up with other players many times, and most of the game is only accomplishable by doing so. You can join a party of up to 4 other people or a raid of up to 39 other people depending on what you're trying to do. In WoW there are essentially two types of play: PvE and PvP. PvE stands for "player versus environment," and basically means non-competitive gameplay against AI-controlled monsters WITH other people. PvP stands for "player versus player," and is the true multiplayer competition aspect of the game; in PvP you strive to kill people of the oppossing faction for honor in order to get gear and such (or just for fun). It's not as if you have to choose, as each aspect of gameplay is interchangeable depending on what you want to do that moment, but many players will focus on one aspect over the other. Anyhow, the big reason WoW gets a huge thumbs-up in the gameplay department is because of its ease. You don't have to be, by any standard, a pro at MMORPG's or RPG's (or even video games) to play WoW and enjoy yourself. The game outlines the rules and gives tips very clearly, enabling noobs to get into the game very quickly and easily. Taking and completing quests, combat, getting into groups, and making items are all very easily accomplished, but they're still fun to do. Granted, the game isn't completely mindless, and in raids/pvp it takes skill and wit to master the game. ***So, basically, WoW's gameplay is great because it's: easy, simple, fun.***
Graphics:
The graphics in WoW are by no means amazing. However, you have to take into account that it's a vast MMORPG. If it had graphics of the quality of Half-Life 2, no one's computer would be able to run it effectively. Even so, the fully 3D graphics are still impressive on some scale. The bloom light effects and terrain-based bump mapping look nice if you've got the hardware, and it's more artistic/cartoony style as opposed to realism is refreshing. The models are not uber high-poly, but they do feature some impressive detail. The environments (especially those featured in Outland in the upcomming expansion) are breathtakingly beautiful at times.
Sound: As with the graphics, WoW's audio is nothing innovative or amazing, but it's just plain good. The music is fully orchestrated (or at least it sounds so) and epic, and the limited voice-acting is funny and entertaining. The various sounds on the monsters, weapons, weather effects, and spellcasts make the world sound very alive.
Value:
Essentially, WoW is one of those games that owns your soul. I only (only, lol) have two level 60's, and since starting my mage in May of 2006, i've logged on 720 (that's one month of playtime in a span of six months) hours to him alone, that's not even taking into account my lvl 60 warrior and my various other alt characters that I've made. The game is very easily addicting, and I strongly caution you to limiting your time to an hour or two a day or only on weekends. My grades in school and my social life HAVE suffered from WoW, but that's no reason for you not to buy it. I have bad time management, but that in no way means this game isn't amazingly good.