From
Barry R. Levin's Biblionotes:

KING, STEPHEN. TWICE THE POWER.
Kent: Hodder & Stoughton. 1991. "Presentation proof." This volume contains Stephen King's novel, NEEDFUL THINGS, as well as the second story from King's FOUR PAST MIDNIGHT — "Secret Window, Secret Garden." (Another state of this "presentation proof" is reported to contain yet another story from FOUR PAST MIDNIGHT.) This volume was produced in order to promote the British first edition of NEEDFUL THINGS and the British first paperback edition of FOUR PAST MIDNIGHT. The "presentation proofs" are the only form the title twice the power takes. Wrappers.
http://www.raresf.com/bnotes.html

I have to add that I've never seen a copy with a story other than "Secret Window, Secret Garden" in this proof.

John