This is one of the less common paperbacks. While it is only moderately
difficult to locate the price is relatively high, especially if the book is in good shape
and has no bookstore stamps, but still within the casual collector's price
range. It is an expanded version of his novella "The Mystery of His Flesh",
which was originally published in
The Magazine of Fantasy and Science Fiction
in July 1970.
You have a first edition of this paperback if it states on the copyright page
"First Printing : July 1970".