... A Rare Benedictine by Ellis Peters

Synopsis: Finally, Brother Cadfael's many fans can discover the chain of events that led him into the Benedictine Order! Lavishly illustrated, these three tales show Cadfael at the height of his sleuthing form. "Three classic stories featuring Brother Cadfael . . . whose powers of deduction are practically miraculous."--

...An Excellent Mystery by Ellis Peters

Synopsis: In 1141, two monks have arrived in Shrewsbury from Winchester, where their abbey was destroyed. Now Brother Humilis, who is very ill, and Brother Fidelis, who is mute, must seek refuge at Shrewsbury. And from the moment he meets them, Brother Cadfael senses something deeper than their common vows binds these two brothers. And as Brother Humilis's health fails, Brother Cadfael faces a poignant test of his discretion and his beliefs as he unravels a secret so great it can destroy a life, a future, and a holy order.

.. St. Peter's Fair by Ellis Peters

Synopsis: When a merchant bound for St. Peter's Fair is found with a slender dagger piercing his heart, Brother Cadfael is on the case. Two murders later, he realizes that no one--least of all the merchant's lovely niece--is safe.

.. The Leper of Saint Giles by Ellis Peters

Synopsis: A savage murder interrupts an ill-fated marriage set to take place at Brother Cadfael's abbey, leaving the monk with a terrible mystery to solve. The key to the killing is hidden among the inhabitants of the Saint Giles leper colony, and Brother Cadfael must ferret out a sickness not of the body, but of a twisted mind.

...Monk's Hood by Ellis Peters

Synopsis: When a visitor to the abbey dies, Brother Cadfael faces a personal drama. For not only was the man poisoned by monk's hood oil, made in Cadfael's own laboratory, the dead man's widow is also the woman to whom Cadfael was betrothed before he took his vows.

Monk's Hood/Cassettes by Ellis Peters

.. The Devil's Novice by Ellis Peters

Synopsis: In the autumn of 1140 the Benedictine monastery at Shrewsbury finds its new novice Meriet Aspley a bit disturbing. The younger son of a prominent family, Meriet is meek and biddable by day, but his sleep is rife with nightmares so violent that they earn him the name of "Devil's Novice." Shunned by the other monks, Aspley attracts the concern of Brother Cadfael. Then a body appears, that of a young priest last seen at the Aspley estate. Can Meriet be involved in the death? As events take a sinister turn, it falls to Brother Cadfael to detect the truth.

... Brother Cadfael's Penance : The Twentieth Chronicle of Brother Cadfael by Ellis Peters

Synopsis: While Cadfael has bent Abbey rules, he has never broken his monastic vows--until now. Word has come to Shrewsbury of a treacherous act that has left 30 of Maud's knights imprisoned. All have been ransomed except Cadfael's secret son, Olivier. Conceived in Cadfael's soldiering youth and unaware of his father's identity, Olivier will die if he is not freed.

...Pilgrim of Hate by Ellis Peters

Synopsis: Preparing to celebrate an important anniversary for the Abbey at Shrewsbury, medieval herbalist and Benedictine monk Brother Cadfael finds himself trying to solve the murder of a Winchester knight believed to have treasonous loyalties.

....Dead Man's Ransom by Ellis Peters

Synopsis: The year is 1141 and civil war continues to rage. When the sheriff of Shropshire is taken prisoner, arrangements are made to exchange him for Elis, a young Welshman. But when the sheriff is brought to the abbey, he is murdered. Suspicion falls on Elis, who has fallen in love with the sheriff's daughter. With nothing but his Welsh honor to protect him, Elis appeals to Brother Cadfael for help. And Brother Cadfael gives it, not knowing that the truth will be a trial for his own soul.

....The Raven in the Foregate; Ellis Peters

Synopsis: It is Christmas, A.D. 1141, Abbot Radulfus returns from London, bringing with him a priest for the vacant living of Holy Cross, also known as the Foregate. The new priest is a man of presence, learning, and discipline, but he lacks humility and the common touch. When he is found drowned in the millpond, suspicion is cast upon a young man who arrived with the priest's train and was sent to work in Brother Cadfael's garden. Indeed, he is soon discovered to be an impostor. To Brother Cadfael, now falls the familiar task of sorting out the complicated strands of innocence and guilt.

..The Rose Rent by Ellis Peters

Synopsis: In honor of her husband, young, beautiful, and wealthy widow Judith Perle donates a house to the Abbey at Shrewsbury--for the annual rent of one white rose. Judith has no shortage of suitors, and if she remarries, her dowry would be all the greater if the house were returned due to non-payment of rent. So when a priest charged with delivering the rose is found murdered, and the rose bush is found hacked to pieces, Brother Cadfael finds he must root out a killer.

....The Sanctuary Sparrow by Ellis Peters

..The Holy Thief by Ellis Peters

Synopsis: The 19th chronicle of Brother Cadfael. In the chill autumn of 1144, rising flood waters endanger the sacred remains of St. Winifred, the abbey's most cherished possession. When the bones disappear and a corpse is found, Brother Cadfael needs his prayers answered to catch a killer.

The Brothers of Gwynedd : Comprising, Sunrise in the West, the Dragon at Noonday, the Hounds of Sunset, Afterglow and Nightfall by Edith Pargeter, Ellis Peters

.....Brother Cadfael's Herb Garden : An Illustrated Companion to Medieval Plants and Their Uses by Robin Whiteman, Rob Talbot, Ellis Brother Cadfael chronicle Peters

Brother Cadfael, the enthusiastic gardener and herbalist created by Ellis Peters, was renowned for his great knowledge of plants, especially the exotic varieties he had brought back from his extensive travels to the Holy Land and elsewhere. The herb garden was his particular domain, and as the abbey's apothecary and healer he was often to be found tending the plants there, or brewing up potions in his workshop. This beautifully illustrated book now re-creates Brother Cadfael's herbal kingdom. It begins by tracing the history of herbals and herb gardens, and places Cadfael's herb garden in the context of the monastic gardens at Shrewsbury. It describes Cadfael's work as a healer, one of his duties being to supply medicines for the infirmary, and traces a typical year in the life of this devoted herbalist. The A-Z section of the book lists all the herbs and plants mentioned in The Brother Cadfael Chronicles, and explains their various uses in medieval times - before the days of modern antibiotics, medicines, and flavorings, herbs and herbal remedies were an essential part of the medieval world. Most could be found in Cadfaels' beloved herb garden, or in the surrounding fields and hedgerows, faithfully evoked in full color in this unique and informative book.

And on the distaff side I offer Sister Fidelma. A nun in the Celtic ( keltic ) church, A.D. 664.
If you like Brother Cadfael you'll like these.

....Absolution by Murder : A Sister Fidelma Mystery by Peter Tremayne

Synopsis: In A.D. 664, when someone murders the Abbess Etain during the synod between the Roman and Celtic churches, Sister Fidelma of the Celtic Church and Brother Eadulf of the Roman must find the killer and prevent civil war.

Shroud for the Archbishop : A Sister Fidelma Mystery by Peter Tremayne

Synopsis: An archbishop designate of Canterbury is murdered in his chambers in the Lateran Palace in Rome in the autumn of A.D. 664, and Sister Fidelma of the Celtic Church, along with Brother Eadulf of the Roman Church, are called in to investigate.

Suffer Little Children : A Sister Fidelma Mystery by Peter Tremayne

Synopsis: In the seventh century A.D., the murder of a high cleric threatens to result in war between two of Ireland's kingdoms. Sister Fidelma is summoned by the dying king to both solve the murder and prevent war. But Fidelma soon discovers that there are far more sinister forces at work than mere political intrigue.