The best science fiction challenges our imagination, pushing it to expreme limits. In this anthology of stories containing some of the best science fiction produced over the last 50 years, 20 leading authors of the genre ask the question "What if...?" and give their own fascinating versions of the changes that will happen in the centuries to come.

Edited by Mike Ashley.
Contents:

• Ulla, Ulla by Eric Brown
• Deathday by Peter F. Hamilton
• The Infinite Assassin by Greg Egan
• Anachron by Damon Knight
• Firewatch by Connie Willis
• At the "Me" Shop by Robert Reed
• Vinland the Dream by Kim Stanley Robinson
• A Ticket to Tranai by Robert Sheckley
• The Exit Door Leads In by Philip K. Dick
• What Have I Done? by Mark Clifton
• Finis by Frank L. Pollock
• The Last Days of Earth by George C. Wallis
• Approaching Perimelasma by Geoffrey A. Landis
• The Pen and the Dark by Colin Kapp
• Inanimate Objection by H. Chandler Elliott
• The Very Pulse of the Machine by Michael Swanwick
• High Eight by Keith Roberts
• Shards by Brian W. Aldiss
• Except My Life³ by John Morressy
• Into Your Tent I’ll Creep by Eric Frank Russell
• A Death in the House by Clifford D. Simak
• Refugium by Stephen Baxter