I've never played any Plants vs. Zombies games. The PopCap site says this on their: Plants vs. Zombies page:
Get ready to soil your plants! Again! PopCap's fun-dead game of the year is updated and expanded with 20 new achievements and the interactive Zombatar™. Make your very own zombie, then watch it come to "life" in your game!
Stop 26 types of zombies dead in their tracks with your arsenal of 49 zombie-zapping plants! Battle through 50 Adventure levels, 20 Mini-Games, plus Puzzle and Survival modes. Or dig into the zombie-free Zen Garden. The fun never dies!
Looks like this is a sequel. Is there another version that I should get to get into the series? Or is this the original, with extra features?