This is probably a copyright violation, which ordinarily I'd oppose since I'm an author and depend on royalties. However, the book is out of print. Used copies are going for astronomical sums. Download it and read it before the link vanishes.
If the author gets after you, don't complain. Send him the amount of royalty he'd get from the sale of the original hard-cover version. As I recall, I paid $25 for it; at 10% he's entitled to $2.50. Don't begrudge it to him.
In any case, read it and be warned.