Is this a good bike to buy?

It's probably ok for the price. You could find a much better used bike for about the same price I think. This type of bike is generally a cheaper, budget-oriented bike so it has cheaper less reliable parts on it. They are fine for riding around town, but if you try to do serious mountain biking they probably won't hold up. A lot of people say never to buy the cheaper bikes like this, but they are fine for casual use, or even pretty constant use if you just don't expect it to last for a long time. Most people are not riding off road on real mountain bike trails so these bikes are fine.