“THE HOLLOW-EYED ANGEL,” by Janwillem van de Wetering; Soho Press Inc., New York; 282 pages; $22 hardcover.

“THE MERRY WIDOW FOX-TROT,” by Donald Mortland; North Country Press, Unity; 212 pages; $14.95 paperback.

“Most of what is out there … we’ll never know about, unless we learn to pay attention,” says Janwillem van de Wetering through one of his detectives in his latest mystery, “The Hollow-Eyed Angel.” This is the 13th in his enjoyable series involving his Amsterdam policeman, Sgt. Rinus de Gier, Adj. Henk Grijpstra, and their mentor, the Commissaris.

This time around, the Commissaris, who is ailing, finds himself in New Amsterdam, or New York City, attending an international police convention, listening to lectures on “modes of crime,” but also investigating the murder of a fellow Dutchman whose mutilated body was found in bushes in Central Park. De Gier joins him; and the story goes back and forth between the two detectives in New York and Grijpstra, who remains in old Amsterdam making inquiries of the dead man’s acquaintances and his gay nephew who is a hairdresser and volunteer cop.

The victim was Bert Termeer, who was a used-book dealer in Holland, but who in New York specialized in “used spiritual books” and pornography. He is described by his landlord, Charlie Perrin, as “a dignified gentleman frolicking in childlike joy.”

Before he was murdered, “Termeer would wander about the city, evenings and weekends, searching for the right moments, the right locations” to put on his shows that would entice people into his world. Termeer posed as a well-dressed prophet, a New York street character; but to the New York police, he was just an eccentric bum who was accidentally kicked by a policewoman’s horse, which brought on a fatal heart attack.

“The Hollow-Eyed Angel” of the title appears in a recurring nightmare that the Commissaris keeps having about a beautiful Dutch streetcar driver with long legs and empty eye sockets. She’s the angel of death, but of whose death?

The fun of reading van de Wetering — and he is great fun for serious readers — is never the plot, but the clever plays on words, his wonderful digressions on society and the state of man; and what The New York Times has termed his “deft composites of police procedural, social and character studies, puckish humor, and Zen Buddhist philosophy.”

Van de Wetering is a Dutchman who has been haunted since he was a teen-ager by the murders of his Jewish classmates during the Holocaust. He has searched the world for answers to that horror. He has worked as a policeman in Amsterdam and he has been a Buddhist in Japan. He has lived all over the world, meeting his wife, Juanita, in Colombia and finally settling down in Maine in 1975. About his work, he has said, “Look, I just want to know why I am here, and why the world’s here. What are we all doing here, anyway?”

In his latest novel, he mentioned how Bert Termeer once tried to work his act in the parks of Bangor, Maine, without much success; and he tells about how one of the best things to do in life is to watch the seals off the Maine coast.

As van de Wetering fans know, his detectives are wonderfully human characters who say such things as: “The truth … stares me in the face, and my mind rushes off to look for lies. How many times has this happened?”

Grijpstra composes poetry, which he recites from time to time. One of his poems begins: “Pure emptiness illuminated by the glow of the void.” And, while the Commissaris is staying at a fancy hotel overlooking Central Park, he eats his meals at a Haitian restaurant called Le Chat Complet, where every time a cat walks by, three musicians behind the counter start harmonizing.

“Death never seems to be pleasant, birth isn’t fun, either, but there is the quest in between,” says the author; and the quest with van de Wetering and company is always unpredictable, amusing, intelligent and fascinating.

An Amsterdam book dealer, who knew the murdered man, says to the detective at one point: “That’s the infinite out there. The great secret … You think you can put infinity into books?” The author answers by saying, “Maybe by creating seemingly crazy circumstances … by creating a crack in the regular world regular folks build up for themselves. Then slip through it.”

While Janwillem van de Wetering writes about aging detectives nearing retirement, most of the characters in Donald Mortland’s “The Merry Widow Fox-Trot,” subtitled “And Other Tales of Life in Maine After Sixty,” are way beyond retirement. There are 15 stories that take place from the 1930s to the present, but since Mortland grew up in Searsport and taught English at Unity College for many years, I suspect the Maine towns in his tales are based on those he has known best.

Take the first story, “A Tangled Web,” for instance. Set in Pendleton, a coastal town near Camden, one pictures Searsport, famous and infamous for its many antique dealers and yard sales along Route 1. The story is concerned with two elderly sisters, Prudence and Felicity Partridge, who turn their old house into an antique gallery where the ladies dress up in old-fashioned get-ups and soak the tourists on their sales. This amusing tale of deception has a touch of “Arsenic and Old Lace” to it.

The title story is also about deception wherein Abby Edison, the “merry widow,” pretends that after her husband died she was left well off when she wasn’t. She gets involved with a much younger man named Pruitt Frothingham, who had lived with his mother into his 40s.

Anyone who has lived in a small Maine town can appreciate how Abby keeps her money in a bank in Belfast because she knows how the locals who work at the bank know how much money everyone has.

In “Curtain Falls,” we have the case of a man named Miles Dunbar, who owns practically the whole town of Curtain Falls; and he is busy trying to get his own 90-year-old mother to move out of her own house so he can build a golf course on her property.

In “Rented Land,” an 80-year-old farmer trying to keep his farm going rents some of his fields to strangers, who use them for growing marijuana.

With the aging of our society, what’s wonderful about this timely collection is the cumulative portrait of older folks in Maine who are not in nursing homes yet but who are busy living their lives. They are resourceful, feisty, and still full of life.

My only quibbles are concerned with too many characters archly named Prudence, Felicity and Palmer, and everyone using the old Maine expression “gorry.”

Otherwise, “The Merry Widow Fox-Trot” should be a very popular book, not only with senior citizen groups, but for anyone interested in how small-town Maine communities used to function.