Crosstime/Blake Walker Series by Andre Norton

When Blake Walker foiled a murder attempt on one of his neighbors he somehow found himself drafted into a frantic chase for a dangerous criminal - through the almost infinite levels of alternate Earths.It was a chase that would take him through level upon level of unknown dangers in search of a ruthless genius who had found our Earth the perfect place to begin his series of conquests.If Walker succeeded, he would save Earth... moreWhen Blake Walker foiled a murder attempt on one of his neighbors he somehow found himself drafted into a frantic chase for a dangerous criminal - through the almost infinite levels of alternate Earths.It was a chase that would take him through level upon level of unknown dangers in search of a ruthless genius who had found our Earth the perfect place to begin his series of conquests.If Walker succeeded, he would save Earth. If he failed, his homeworld could be enslaved, and he could be trapped on an alien Earth! less

A DESPERATE SEACH ACROSS PARALLEL WORLDSAn orphan, Blake Walker has never really known who he was, and his strange flashes of intuition have always set him apart from those who raised him and everyone else he has known. Acting on one of those flashes, he prevented a murder. But neither the assailant nor his intended victim were from the world Walker had always known—he had stumbled onto the greatest secret of the ages... moreA DESPERATE SEACH ACROSS PARALLEL WORLDSAn orphan, Blake Walker has never really known who he was, and his strange flashes of intuition have always set him apart from those who raised him and everyone else he has known. Acting on one of those flashes, he prevented a murder. But neither the assailant nor his intended victim were from the world Walker had always known—he had stumbled onto the greatest secret of the ages.Our Earth is only one of an infinite number of Earths, each with a slightly different history from the others, each separated from the others in a crosstime dimension. Walker was drafted into a frantic search for a madman from an advanced Earth who desires to be an absolute ruler of men. The would-be tyrant has chosen our Earth as the place where his reign will begin.And, if the powerful technology he controls does not give him complete control of the planet, he will not hesitate to destroy it utterly. . . .At the publisher's request, this title is sold without DRM (DRM Rights Management). less

The universe had opened up for Blake Walker when he discovered that his world - our own Earth - was just one of hundreds ranked side by side on alternate timelines, each more strange and wondrous than the other, all coexisting at once, and all available to Blake Walker and the few natives of those other-Earths who could break the barriers between timelines.But Blake's new existence is threatened now - his time-traveling patron's daughter has been kidnapped... moreThe universe had opened up for Blake Walker when he discovered that his world - our own Earth - was just one of hundreds ranked side by side on alternate timelines, each more strange and wondrous than the other, all coexisting at once, and all available to Blake Walker and the few natives of those other-Earths who could break the barriers between timelines.But Blake's new existence is threatened now - his time-traveling patron's daughter has been kidnapped. The engineers who could control the time-travel process are in open rebellion. And Blake himself has stumbled across a plot by a powerful and dangerous band of conspirators to ravage all the Earths in their reach.Blake must stop them. He knows that somewhere in the infinity of time there lies the key to solving this crisis. If he only knew when to look... less