I teach English to 20 Korean adults mostly by means of telephone
conversation. I spend 5 minutes a day for each person, and they are
making good progress. Now I need some English books containing 'topics
for discussion', so that we can discuss the information in English,
which will make our conversation more enjoyable. I want to avoid
religious as well as political topics.

What about their subscribing to a basic English language magazine?

http://www.studioclassroom.com/h_products.htm

I think NT$ 1400 is about US$ 42 for an annual subscription.

I teach ESL (English as a second language) at the American Language
Center in Rabat, Morocco. I use several books depending on the level
of my students: "Interchange" for beginner students, "Crossroads" for
intermediate students, and "Inside out" (my personal favorite) for
upper intermediate and advanced students. These books (especially
Inside out) have quite a few reading sections with a wide variety of
topics that you may utilize for your discussions, and they usually
steer away from religion and politics. "Inside out" is published by
MACMILLAN, the authors are JONES, CERI & BASTOW, TANIA, and the ISBN
for the advanced version is 0333917405. I also tutor diplomats at
embassies and consulates (including the Korean ones), and there we
usually pick up on something on the news: storms in the pacific,
global warming, a publicized divorce case, anything really that
catches the student's attention.

I hope this helps.

Cheers, expertopinion.

Although you requested the title of a books, would you also accept a
website of discussion topics and questions? If so, check out the
following website
http://iteslj.org/questions/

Happy chatting!