Michael Moorcock 
Champion of Garathorm [EPUB ebook] 

After journeying across the multiverse with other manifestations of the Eternal Champion, Dorian Hawkmoon is stunned to discover that he has returned to a version of his world in which it was his friend and ally, Count Brass, who survived the Battle of Londra, rather than Brass’s daughter – and Hawkmoon’s beloved wife – Yisselda. Driven close to madness by the loss of his wife and children (who never existed in this world), he locks himself away in Castle Brass, painstakingly recreating the battle of Londra, in an attempt to discover a version in which Yisselda also survives. But the paths through the multiverse are treacherous…