I recommend
The Confession of St. Patrick. Keep in mind that I am referring to St. Patrick’s Confession, not the one by St. Augustine (although there is certainly nothing wrong with St. Augustine’s, it’s just definitely not a quick read).
I recommend this book to you for the following reasons:
1) It is considered a classic in terms of Catholic spirituality.
2) It is, indeed, a quick read. The linked edition is a pocket-sized book (7" x 4.2" x 0.4") and is a total of 81 pages long. The book, however, also contains St. Patrick’s “Letter to Coroticus” as well as pages of commentary. If one limited oneself to reading only the Confession, it would be about 55 pages long (and the text does not completely fill each page either due to the line format). In other words, 55 pages in this book is a lot less reading than 55 pages in a “normal” book.
3) It is St. Patrick’s autobiography, and is a story about having faith, hope and trust in God in a world where it was far easier to despair. It is also a testimony to the power of forgiveness, because St. Patrick was a slave who escaped from Ireland, and yet was sent by God to return to Ireland as a missionary. Such aspects should generate some good discussions. It is also really interesting to read an account of a saint’s life written by the actual saint.
4) It only costs seven bucks (and there are plenty of very inexpensive used editions available through Amazon as well).