If you're new to CURB YOUR ENTHUSIASM, don't start with Season 4, unless it happens to fall in your lap. Try to start from the beginning. There is actually a subtle progression to the show. Each episode contains both "self-contained" stories, and ongoing issues that develop from show to show, and sometimes from season to season.
But I'm assuming that if you're looking at Season 4, you're already interested in or familiar with CYE. Season 4 is a laugh-riot. I think the season now has the perfect blend of Larry David, the unfortunate victim of circumstance and Larry David, the jerk who brings bad things on himself.
On one hand, Larry tries to be a nice guy. He always seems to enjoy the company of children, for example...in a genuine way. He'll sit down with them and play their games and talk to them like they're actually interesting. To him, there's no one who isn't worth talking with and trying to be friendly with. This is an admirable trait...which always gets him in trouble. On the other hand, Larry never knows when to quit. He'll start on a subject (for example, he begins to suggesting possible "oriental-sounding" names to a secretary who is getting ready to adopt a child), and his riff becomes more and more inappropriate and the signals from the woman become easier and easier to notice, but he blithely rambles on...making an enemy whose disgust WILL come back to bite him.
Often, Larry David is categorized as a misanthrope. To me that's far too easy. What I like about him is that he can go from charming and amusing and genuinely concerned about something (his interactions with his wife, for example) to an overbearing, overopinionated jerk in about two seconds flat. We see him crossing the line, but he never sees it himself. He thinks his complaints or questions are perfectly reasonable. (There's a great scene where he is waiting in a doctor's exam room for the Dr. to appear...so he uses the phone in the room. Doctor [brilliantly under-played by Phillip Baker Hall] explains that the phone is not for a patient's use. David just keeps insisting on knowing why. He tries at one point to restrain himself...but he just can't help it...he's obsessed with getting an explanation!).
The big story of the season is Larry being hired by Mel Brooks to take the lead in THE PRODUCERS on Broadway. It's a bit of a stretch to believe Mel would make such a choice, but if you buy it...you're in for a real treat! Ben Stiller appears in several early episodes and is very funny doing his "slow-burn" schtick. The show has always been great for letting its guest-stars playing themselves turn their whole images upside-down.
It's unfortunate that a typical CYE season only has 10 episodes...but heck, each one packs the laughs of 3 or 4 typical sitcoms into it, so from an entertainment standpoint, you can't beat this show. Every episode makes me laugh out-loud many, many times.
By the way, in case you don't know...these shows ARE NOT FOR KIDS!!! They contain very frank (and funny) language and situations. Strictly for adults. But highly recommended too!!