First note that for each row, the @ represents the same symbol
Which is in fact the unique common letter.
Each describes a three-word phrase:
1. Second LOTR Volume: The Two Towers (LOTR = Lord of the Rings)
2. Branwell's Author Sisters: Charlotte, Emily, Anne (Sisters of Branwell Brontë)
3. Helga's Fellow Founders: Rowena, Godric, Salazar (Founders of the houses of Hogwarts in the Harry Potter series)
4. Dan's Langdon Debut: Angels and Demons (First Dan Brown book featuring Robert Langdon)
5. Crale Cold Case: Five Little Pigs (Agatha Christie novel about the murder of Amyas Crale)
6. Treasure Island Author: Robert Louis Stevenson (No explanation required)
7. Austin Dashwood Romance: Sense and Sensibility (Romantic novel by Jane Austen featuring the Dashwood sisters)
8. Dumas' Musket Men: Athos Porthos Aramis (The Three Musketeers)
Note that for each three-word phrase, there is exactly one (unique!) common letter among the three words, which spells:
ternions (which is really neat since it means 'groups of three')