The correct Roman Catholic sexual position is not, as many might imagine, missionary, infrequent and with the lights out, but "saucy, surprising and fantasy packed".

The bleak traditional view was St Paul's injunction to the Corinthians: "It is better to marry than to burn with passion." However, a Polish priest who has written a surprising bestselling sex manual dubbed the "Catholic Kama Sutra" believes it is better still to marry and burn with passion.

The first edition of the book by Father Ksawery Knotz, a Franciscan from a monastery outside Krakow, titled Seks (in very large letters) and "for married couples who love God" in rather smaller type, has sold out and is being hastily reprinted in Warsaw.

"Every act – a type of caress, a sexual position – with the goal of arousal is permitted and pleases God," he writes. "During sexual intercourse, married couples can show their love in every way, can offer one another the most sought-after caresses. They can employ manual and oral stimulation."

His book has the blessing of the Polish Catholic church and follows the orthodox line in many ways: he firmly addresses only married couples and discourages the use of any form of contraception, saying it can "lead a married couple outside of Catholic culture and into a completely different lifestyle". But within those confines, couples are urged to let rip.

"Some people, when they hear about the holiness of married sex, immediately imagine that such sex has to be deprived of joy, frivolous play, fantasy and attractive positions. They think it has to be sad like a traditional church hymn," he writes. Calling sex a celebration of the marriage sacrament raises its dignity in an exceptional way. Such a statement shocks people who learned to look at sexuality in a bad way. It is difficult for them to understand that God is also interested in their happy sex life, and in this way gives them his gift."

If not shocked, some readers might wonder what a celibate priest knows about the subject. He concedes that a priest writing a book about sex is seen as sensational, but he insists that his experience may be second hand, but it is extensive.

"I talk with a lot of married couples and I listen to them, so these problems just kind of sit in my mind," he said. "I would like for them to be happier with their sex life, and for them to understand the church's teachings so there won't be unnecessary tension or a sense of guilt." He has also run a website offering sexual advice to the devout for the past year.

Warm fulfilling discussions are ongoing about translations into Slovakian, Italian and English editions. The publishers are in ecstasy.