The Queen has said that she is "very grateful" to the nation for its prayers for her in a strong statement of her Christian faith. She says she has felt God's "faithfulness" during 64 years on the throne.

The new insights into Queen Elizabeth II's personal thoughts and Christian faith are in the foreword to a new book.

The Servant Queen and the King She Serves is published by Bible Society, HOPE and LICC to mark her 90th birthday in April.

The Queen says: "I have been – and remain – very grateful to you for your prayers and to God for his steadfast love. I have indeed seen his faithfulness."

She refers to the changes she has seen in her life, which recently saw her become the longest-reigning monarch in British history.

"The extent and pace of change has been truly remarkable," she says. "We have witnessed triumphs and tragedies." She alludes to the current problems in the Middle East, saying that the world is now experiencing "terrible suffering on an unprecedented scale".

The Queen's Christian faith is well-known. In recent years, Her Majesty has referred to her beliefs in public statements, including Christmas broadcasts.

The Servant Queen and the King She Serves highlights the Queen's faith and how it has shaped her personal life and service to the nation. A 12-page schools version has been published by Scripture Union.

Bible Society, HOPE, LICC and Scripture Union are encouraging churches to bring communities together to celebrate the Queen's 90th birthday with thanksgiving services and street parties on Sunday 12 June, giving the book away as a gift to party guests.