This collection originally published as 'Ace science fiction reader'. New York: Ace Books, 1971.
OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
Trilogy of the future: The trouble with Tycho/ [by] Clifford D. Simak; [and], The last castle/ [by] Jack Vance; [and], Empire star/ [by] Samuel R. Delany by Donald Allen Wollheim. ISBN 028397849X. Published by Sidgwick and Jackson in 1972. Publication and catalogue information, links to buy online and reader comments.
![Trilogy of the future: The trouble with Tycho/ [by] Clifford D. Simak; [and], The last castle/ [by] Jack Vance; [and], Empire star/ [by] Samuel R. Delany](http://ecx.images-amazon.com/images/I/41YjoLZV-aL._SL160_.jpg)