Tan Books has some good resources from Doctors of the Church. They have Hell and Its Torments by St. Robert Bellarmine and What Will Hell Be Like by St. Alphonsus Liguouri. The title of the books will interest the modern reader, who is normally fascinated by all things dealing with hell. The fact that it’s a booklet will also be better suited for those who wouldn’t read an entire book. They can be purchased for as little as 75 cents a piece with a bulk order. Another good resource that you may wish to try is a sermon The Little Number of Those Who are Saved by St. Leonard of Port Maurice. This can be found online from various places, but olrl.org provides a four page copy for 10 cents each if you don’t wish to print it yourself. olrl.org is controversial because of its stance against the Novus Ordo Mass, but they have great traditional resources on their websites. The sermon is also controversial as it can drive a scrupulous soul into despair. I believe we need to talk about hell often (albeit prudently) because Our Lord spoke so often of hell, and the doctors and saints of the Church along with approved apparitions of Our Lady are unanimous that the majority of humanity goes there.
Tan Books also has books from the creators of the show Radio Replies (Frs. Rumble and Carty) on Hell and Purgatory. They have bulk prices on these, too. I haven’t checked these out, but I wasn’t terribly impressed with their layout of the booklet I read on Mary and statues. The content was good, and it is laid out as someone basically attacking the orthodox Catholic position on various topics with the authors replying and setting the record straight.