I do not mean to be alarmist, nor to peddle the facile notion of history repeating itself. The world of 1929 was in many respects very different. But there are enough parallels to be instructive. And right now, we need all the instruction we can get.
I have been consulting the best book I know on the subject, Charles Kindleberger's The World in Depression 1929-1939. Last updated in 1986, it makes one point of pressing relevance today: that the depression was not made in America. Then, as now, the crisis was global from the outset and called for global fixing.
One obvious difference is that the market collapse which began in 1929 was in response to a recession which had already started. This time, the recession is following the collapse.