Tim Franklin has a handy way of checking when the Northwestern Bookstore he manages in Edina, Minn., has its marketing finger on the pulse of the reading community.

''I walk through Target,'' he said. ''When I see them selling the same books we are, I know we're on the right track because all they're interested in is numbers [of sales].''

The explosive interest in religious books is reshaping the marketplace. Once largely the domain of niche bookstores, religious books have elbowed their way into mass-market bookstores. While it used to be unusual for a religious book to make a national best-seller list, it's the rare list today that lacks at least one as they jockey for attention in multiple genres: fiction, nonfiction, advice, biography and children's books.

We checked with several local religious bookstores to see which books they're recommending to customers this summer. Here are their suggestions:

• The Shack by William P. Young (Windblown Media, $14.99). A man returns to the abandoned cabin where his daughter was murdered. It's No. 1 on the New York Times paperback trade fiction list. ''It's really not a Christian book,'' Franklin said. ''It's just a book that is based on an interesting theological premise. It started out in secular bookstores. Then our readers found out about it. We actually had to go seek out the book because it didn't come to us through our usual distributors.''

• Dead Heat by Joel C. Rosenberg (Tyndale, $24.99). A political thriller, it's the fifth book in a series that is based on events in the not-too-distant future. ''All of the books in the series have been extremely popular,'' said Rose Hintz, owner of Christian Book Store in Red Wing, Minn. ''He's also got a nonfiction book, Epicenter (Tyndale, $19.99), that's doing well. People who like his novels read it as background'' because it explains the political underpinnings of his stories.

• The Door Within trilogy by Wayne Thomas Batson (Thomas Nelson, $9.99). A youngster visits a magical kingdom ruled by a benevolent king. ''They're like the Harry Potter books, only better,'' said Cindy Fischer, manager of the Wooddale Bookstore in Eden Prairie, Minn.

• DragonSpell, the first of five in a series by Donita K. Paul (WaterBrook, $13.99). A fantasy in which a 14-year-old girl encounters adventures.

• Quiet Strength by Tony Dungy (Tyndale, $26.99). The coach of the Indianapolis Colts reflects on his Super Bowl-winning football team as well as the suicide of his son.

• Finding the Monk Within by Edward C. Sellner (HiddenSpring, $24). This nonfiction book examines how centuries-old monastic values can be applied to modern life. ''The author is a professor at [the College of] St. Catherine,'' said Tim Doran, manager of the three St. Patrick Guild stores. ''This book is doing very well.''

• Thin Places by Mary Treacy O'Keefe (Beaver's Pond Press, $17). Another hot local author, O'Keefe reflects on the deaths of her parents, which were separated by only three months. The book is subtitled Where Faith Is Affirmed and Hope Dwells.

• How to Raise a Jewish Dog by Ellis Weiner (Little Brown, $12.99). Despite its title, it's not a training book. The former National Lampoon editor has shaped a series of doggie ''inner monologues.'' Toots Vodovoz, the owner of Elijah's Cup in St. Louis Park, Minn., has only one complaint about the book: ''Cat people are mad that there isn't a version for them.''

• unChristian by David Kinnaman and Gabe Lyons (Baker, $17.99). The subhead, What a New Generation Really Thinks About Christianity . . . And Why It Matters, sums up this study based on the religious perceptions of people younger than 30.

• The Reason for God by Timothy Keller (Dutton, $24.95). A minister addresses the most common causes of religious doubt.

• The Faith by Charles Colson (Zondervan, $18.99). Stories about courageous Christians throughout history are combined with accounts from Colson's prison ministry.

• Take the Risk by Ben Carson (Zondervan, $19.99). A physician explores how taking risks can lead to a higher calling.

• Love and Respect by Emerson Eggerichs (Thomas Nelson, $22.99). This marriage advice book originally was published in 2004, ''but for the first couple of years, nobody heard of it,'' Northwestern's Franklin said. ''For the last two years, it's been one of strongest nonfiction books. And for the last nine months, it's been one of our best-sellers.''

• Do Hard Things by Alex and Brett Harris (Multnomah Books, $16.99). These twins challenge their fellow teens to refute the low expectations that hound their generation.

• Mother Teresa: Come Be My Light (Doubleday, $22.95) This collection of letters written over her 66-year career was published last fall but continues to be a strong seller.

• 90 Minutes in Heaven by Don Piper (Libri, $12.99). A true story by a man who was pronounced dead at the scene of a car crash, only to return to life an hour and a half later.