Zooloretto seems to suffer a bit from the preconception that, since it's a zoo theme, it must be a "kid's game". While younger players will enjoy the game, it's a great game for adults, too! Zooloretto is, apparently, a successor to Coloretto - but I have never played Coloretto, so I can't comment on similarities & differences.
In Zooloretto, you run a zoo, which (at the start) has 3 enclosures of different sizes. Players take turns randomly drawing tiles (which might be an animal, a vendor stall, or a coin) and placing them on trucks. Instead of drawing a tile, a player may claim the contents of a truck, and add them to his zoo, but he is then out of the round. (There is one truck per player, so each player gets a truck every round. There are 3 spaces per truck.)
Ideally, you want to fill each enclosure with one type of animal, to maximize your points, but you can get points for partly-filled enclosures, especially if there is a vendor stall next to the enclosure. You also lose points if you have animals that you cannot place in an enclosure.
Players can collect coins from the trucks, and as a bonus for filling certain enclosures. Using these coins, a player may expand her zoo, buy unplaced animals from other players, discard animals from her own barn, or re-arrange her zoo. These "money actions" do take the place of a regular draw/claim action, so timing is important.
A few of the animal tiles are marked as fertile males or females. If a player claims a "breeding pair" (a fertile male and female of the same species), they receive a free baby animal tile, which counts the same as a regular animal for scoring purposes.
There are a number of interesting choices to make in the course of a game: Which animals should I collect? Is there too much competition for kangaroos? Will I be safe to take that elephant, even though I don't have room for it, because another player will want to buy it from my barn? Do I take a truck that's not full, to get the tile I want, or do I push my luck and draw another one, in the hope of getting another tile I want? Do I skip a turn to take a money action, or will that mean that someone else will claim the truck I want?
On the negative side, because there are only a limited number of ways to score points, the basic game can seem somewhat limited after a few plays. However, the Zooloretto Expansions provide a very inexpensive way to deal with this. The extra tiles and options in this expansion are just what the game needs. Also available are Aquaretto (which can play as either a stand-alone game, or a big expansion), and Zooloretto XXL. (I've played Aquaretto once as a stand-alone, but I have not played it as an expansion, nor have I played with XXL.)
Zooloretto has a 2-player option that works quite well. It uses 3 trucks, but, instead of 3 spaces each, they have 1, 2, and 3 spaces. If the 3rd truck has any tiles in it when the first 2 are claimed, then these tiles are discarded. This makes the decision of where to place an tile and when to claim a truck more interesting. Additionally, in a 2-player game, each player can expand their zoo twice. Zooloretto frequently hits the table for my wife and me.
What I like:
The game plays quite well for all ages (or, at least, fairly young players).
The gameplay is very easy to explain. (Scoring can be a little tricky, but it's not too bad.)
There's very minimal downtime between turns.
My wife likes it!
What I don't like:
In the basic game, there are not a lot of different options in gameplay strategy. However, the expansions fix this problem very nicely.