Diablo II may not look like Crysis, but it has enough addicting gameplay to keep anyone satisfied.
Lord of Destruction is an expansion set to Diablo II that adds an entirely new act, along with an increased stash, 16 additional item sets, elite items, ethereal items, a mini-map function, character-specific items, weapon swapping, new hireling options, more hotkeys, and a plethora of more items through the addition of prefixes and suffixes. LOD also updates and fixes numerous aspects of the original including several class skills.
If you've bought Diablo II, then I strongly recommend buying LOD, as it will add several more hours of gameplay and a load of extra features, most detailed above. The new quests in Act V are more or less the same as quests in the other acts. Kill this creature or gather this item seems to be the order of the day. The quest rewards however are, in my opinion, some of the best in the game. One quest even yields the ability to customize a weapon with your name. The city that you receive these quests from is named Harrogath. The people of this city are currently at war with Baal, the final surviving Prime Evil, and it is removing this rather large thorn from the side of the people of Harrogath that composes the main point of Act V. Harrogath has all the essentials: a healer, a smith, a gambler, and, of course, Deckard Cain. Also, there is a man named Qual-Kehk who will hire out Barbarian warriors to aid you in battle (but only after you complete a quest).
All in all, if you've played Diablo II, and loved it, then this game is more or less Blizzard's way of loving you back. If you don't own Diablo II, then I would suggest buying it and then buying this, or do what I did and get the Battle Chest. If neither of this options appeals to you, then, I'm sorry Diablo, I failed you. Have Mercy!