Original: The collaboration with Irving was important for Stoker and through him he became involved in London's high society, where he met James Abbott McNeill Whistler and Sir Arthur Conan Doyle (to whom he was distantly related).
Simplified: The collaboration with Irving was very important for Stoker. Through him he became involved in London's high society, where he met, among other notables, James McNeil Whistler and Sir Arthur Conan Doyle.