Sentence:  But let's suppose your fan activities are confined to writing scholarly treatises on the Sources Used by H.P. Lovecraft in creating his Cthulhu Mythos, or deadly-serious lit-ry criticism of the latest Ace paperbacks [...]. In this case, you may very well be dismissed as an eggheady old <WSD>Sercon</WSD>. 
Meaning of the word marked with <WSD> tags:  A sercon fan; a fan interested in intellectual, rather than fannish, matters.