Renault's Alexander is one of the most complex and haunting fictional characters, and this book (the 2nd of the trilogy which began with Fire from Heaven and continues with Funeral Games)is probably the most accessible. It follows Alexander's last years of conquest in Persia and the East, and is told by Bagoas, the Persian eunuch who once served Darius, King of Kings, and so is won by Alexander along with the rest of Darius' kingdom and personal possessions.
The love that grows between Alexander and his 'Persian boy' is romaticised and stops just short of tipping over into Mills & Boon territory, but is effectively offset both by the parallel relationship with Hephaistion, and the military conquest of the East, the hardship and the conflicts that it engenders amongst the native Macedonians who have been away from home for over 10 years.
Renault does a fabulous job of integrating the ancient sources while never letting them inhibit her imagination in the slightest, and 'her' Alexander has been hugely influential in the way that he is received and understood today. Not that I'm claiming that this is great history - it's not and isn't supposed to be. But it is great fiction.