Semi-official Chronology for the books:
Pre First War
The Last Guardian
Rise of the Horde
Pre Second War
Tides of Darkness (Actually the story of WC2, hence the title)
Beyond the Dark Portal (Actually the story of WC2's expansion, hence the title)
Pre Third War
Lord of the Clans
Day of the Dragon
War of the Ancients Trilogy (Although this covers the war of the ancients it is an alternate timeline of those events that are set at this point in the Rhonin stories)
Night of the Dragon
Pre World of Warcraft
Cycle of Hatred
Stormrage
Other
The Arthas book covers events from WC3 to World of Warcraft: Wrath of the Lich King.