I have some bad news about the copyright.
I did some Googling, and the Browne Popular Culture Library has a box of correspondence betweem Margaret Millar and Will Levinrew for the period 1911 - 1976. This rather suggests that Mr Levinrew was alive in 1976 (given that authors tend to stop writing when dead). If so, all his works are still in copyright everywhere.
Therefore, it would not be a good idea to upload the book here. This is a pity because it sounds interesting. We shall just have to wait till some time after 1 January 2027.
Here's the link:
http://www.bgsu.edu/colleges/library/pcl/page39334.html
Go towards the bottom of the page. The correspondence is the first item in box 4.