About 20 years ago, when they were new, I bought some Tor Science Fiction doubles.  You know, they contained two novellas each, were printed back to back with two covers - sort of like the earlier Ace Doubles.  After some time I realized it was looking like a collection, and I started hunting for more at used book stores, and trading online at bookcrossing, sf-books, and paperbackswap.  In the past 2 or 3 years, they have become almost impossible to find that way, so I finally threw in the towel and ordered the last four through Amazon.com partners.  So, pardon me, while I do a little victory dance here. 

Here's the list.

Congratulations on completing your collection.  That's quite a list.  I don't think I have read more than four of those, which is to say, four halves.

LOL! That is quite impressive. . . all I've read is The Girl Who Was Plugged In, though I think the other two Tiptree novellas are in Her Smoke Rose Up Forever, which I just got about a month ago here. . . at least, I'm positive one of them is. And I think my parents have a couple of those doubles in their library, so if I wanted to I could read them as well. . . but I bet most of those novellas have fallen completely out of print. :( Kudos for capturing them all!

Congrats!  I always liked those doubles.   You've got some good stories there.   It's interesting what authors/stories they pick to go together.  I have never read anything by Biggle.  Unless maybe a short story in some anthology.  I wonder if he's out of print altogether.  I keep looking in used book stores but we don't have any really good ones around here.