Complex sentence: Lovecraft was enthralled by New York, and in what was informally dubbed the Kalem Club, acquired a tight group of supportive friends, who encouraged him to submit stories to "Weird Tales".
Split into simpler sentences: Lovecraft was enthralled by New York, and in what was informally dubbed the Kalem Club, acquired a small circle of friends. Kalem was a tight group of supportive friends who encouraged him to submitt stories to "Weird Tales".