How much you like this game depends on you.
First of all, this and it's other GBA Dogz counterpart are the only dog simulations for GBA. I would go for Dogz Fashion if I had to do it all over again, because looking at the site, it looks more in depth and longer.
The game starts out with being a child getting ready for your first dog. You can visit two pet shops to look for your perfect puppy. You have as much time as you need, don't worry. There are 18 breeds to choose from, most repeat in the pet shop. If you continue moving between the pet shops, the dogs will change. [Btw, if you want a dog, don't go to the other shop to compare, when you get back the dog will be gone and replaced with another choice.]
After choosing your puppy you take it home and your game parents tell you how long you have with puppy, you name your puppy, and they go over the basics. They'll tell you how to train, where the vaccuum to clean up trash is, where the puppy potty is, how to feed puppy, etc.
You get 21 days to create a bond with your puppy and complete it's training. This is where the downfall is. Training is extremely easy. You just repeat the command over and over, your character will say something about puppy learning quickly, and after several tries your puppy will get it. You can tell how well the puppy is learning by how many question marks appear over his/her head. Three means he doesn't understand at all, two means he's getting there, and one means he's almost there. It might take five or six tries to get through each question mark phase. After your puppy learns sit and stay, you can take your puppy for a walk. Some people might tell you that you have limited walking time, but you don't. You can take your puppy for a walk as long as you want, because time basically stops when you take your puppy for a walk. You can only walk between the hours of 3 PM and 6 PM though. When you go for a walk, you can go to either pet stores you saw in the begining of the game. You can't purchase another puppy though, sorry. One will sell toys, fancy potties, and pretty beds. The other will sell nutrious dog foods and drinks. You can also visit a large dog park where, if you buy a ball, tug toy, or frisbee, you can play with your dog. Walking was my favorite part of the game, especially playing in the park.
Later in the game your game parents will start giving you things like CDs you can play on the stereo in the living room (the music does get a little repetetive after a while, it's a nice change), books, and send you out to do errands. It's a cute touch to the game, and gives you something to do.
Overall, the game only lacks because of time. Days are short, it takes almost a week if you're lucky to get your dog ready to take a walk, and most time spent is with your game parents. You have to eat breakfast and dinner with them, which takes a lot of time out of gameplay, and your bed time is at 8PM. And althought there is "Always Together Mode", where if you cared for your dog well enough you can play with your dog anytime, you can't take walks and you're game parents are gone. Which is actually kind of lonely, even though they get annoying in the game itself.
If the game had been longer, or was infinite game play, it would have been better in my book. But starting over is really frustrating, therefore it's like a one time only game for me. It might be different for you, or whoever you purchase the game for. I'd say if you purchase this version, it would be better for a younger child. But it appealed to me aswell, so it really depends on what kind of person you are and what you like.