Dookie is Green Day's 3rd and arguably most popular album to date, being released in February 1994.
If you have listened to Green Day's more recent albums (American Idiot/21st Century Breakdown) you will notice that this is a completely different sound, which I in all honesty, I prefer. However if you haven't heard Green Day before then this is definitely the album to start with, as in my opinion, it is their best work to date.
I enjoyed listening to practically every song on this album - they all have annoyingly catchy tunes (ones that will stick in your head for weeks) and brilliant lyrics from Billie Joe. Many of these songs come from his and the other band members' experiences, notably Basket Case and Welcome To Paradise, and this really shows through.
It is difficult to pick out the best songs from this album, but at a push I would give Basket Case the top spot, followed by Pulling Teeth and Emenius Sleepus, which was written by Mike Dirnt (Bass).
I highly recommend having a listen to a preview of a track or two before you buy the album, as it you like one song from the album chances are you will like the rest, otherwise, probably best to steer clear.